Remove superfluous environment variables in test configurations.

The read barrier configuration is enabled by default, so we can remove
all environment definitions setting `ART_USE_READ_BARRIER` to `true`.

Test: art/test/testrunner/run_build_test_target.py art-test
Test: art/test/testrunner/run_build_test_target.py art-ndebug
Test: art/test/testrunner/run_build_test_target.py art-interpreter
Test: art/test/testrunner/run_build_test_target.py art-interpreter-access-checks
Test: art/test/testrunner/run_build_test_target.py art-jit
Test: art/test/testrunner/run_build_test_target.py art-pictest
Test: art/test/testrunner/run_build_test_target.py art-gcstress-gcverify
Test: art/test/testrunner/run_build_test_target.py art-read-barrier
Test: art/test/testrunner/run_build_test_target.py art-read-barrier-gcstress
Test: art/test/testrunner/run_build_test_target.py art-read-barrier-table-lookup
Test: art/test/testrunner/run_build_test_target.py art-tracing
Test: art/test/testrunner/run_build_test_target.py art-interpreter-tracing
Test: art/test/testrunner/run_build_test_target.py art-forcecopy
Test: art/test/testrunner/run_build_test_target.py art-no-prebuild
Test: art/test/testrunner/run_build_test_target.py art-no-image
Test: art/test/testrunner/run_build_test_target.py art-interpreter-no-image
Test: art/test/testrunner/run_build_test_target.py art-relocate-no-patchoat
Test: art/test/testrunner/run_build_test_target.py art-no-dex2oat
Test: art/test/testrunner/run_build_test_target.py art-preopt
Test: art/test/testrunner/run_build_test_target.py art-gtest
Test: art/test/testrunner/run_build_test_target.py art-gtest-read-barrier
Test: art/test/testrunner/run_build_test_target.py art-gtest-read-barrier-table-lookup
Bug: 62611253
Change-Id: I9926943631927b2056aa51ebaeb3ace263d50c1c
diff --git a/test/testrunner/target_config.py b/test/testrunner/target_config.py
index 40dc02e..b323ddc 100644
--- a/test/testrunner/target_config.py
+++ b/test/testrunner/target_config.py
@@ -24,10 +24,7 @@
 
     'art-test' : {
         'make' : 'test-art-host-gtest',
-        'run-test' : [],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+        'run-test' : []
     },
 
     'art-test-javac' : {
@@ -38,35 +35,20 @@
     # (calls testrunner which builds and then runs the test targets)
 
     'art-ndebug' : {
-        'run-test' : ['--ndebug'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+        'run-test' : ['--ndebug']
     },
     'art-interpreter' : {
-        'run-test' : ['--interpreter'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+        'run-test' : ['--interpreter']
     },
     'art-interpreter-access-checks' : {
-        'run-test' : ['--interp-ac'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+        'run-test' : ['--interp-ac']
     },
     'art-jit' : {
-        'run-test' : ['--jit'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+        'run-test' : ['--jit']
     },
     'art-pictest' : {
         'run-test' : ['--pictest',
-                      '--optimizing'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+                      '--optimizing']
     },
     'art-gcstress-gcverify': {
         'run-test': ['--gcstress',
@@ -90,7 +72,6 @@
         'run-test': ['--interpreter',
                   '--optimizing'],
         'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
             'ART_HEAP_POISONING' : 'true'
         }
     },
@@ -102,7 +83,6 @@
                       '--optimizing',
                       '--gcstress'],
         'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
             'ART_HEAP_POISONING' : 'true'
         }
     },
@@ -110,7 +90,6 @@
         'run-test' : ['--interpreter',
                       '--optimizing'],
         'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
             'ART_READ_BARRIER_TYPE' : 'TABLELOOKUP',
             'ART_HEAP_POISONING' : 'true'
         }
@@ -162,54 +141,30 @@
         }
     },
     'art-tracing' : {
-        'run-test' : ['--trace'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+        'run-test' : ['--trace']
     },
     'art-interpreter-tracing' : {
         'run-test' : ['--interpreter',
-                      '--trace'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
-        }
+                      '--trace']
     },
     'art-forcecopy' : {
-        'run-test' : ['--forcecopy'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
-        }
+        'run-test' : ['--forcecopy']
     },
     'art-no-prebuild' : {
-        'run-test' : ['--no-prebuild'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
-        }
+        'run-test' : ['--no-prebuild']
     },
     'art-no-image' : {
-        'run-test' : ['--no-image'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
-        }
+        'run-test' : ['--no-image']
     },
     'art-interpreter-no-image' : {
         'run-test' : ['--interpreter',
-                      '--no-image'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
-        }
+                      '--no-image']
     },
     'art-relocate-no-patchoat' : {
-        'run-test' : ['--relocate-npatchoat'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
-        }
+        'run-test' : ['--relocate-npatchoat']
     },
     'art-no-dex2oat' : {
-        'run-test' : ['--no-dex2oat'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
-        }
+        'run-test' : ['--no-dex2oat']
     },
     'art-heap-poisoning' : {
         'run-test' : ['--interpreter',
@@ -229,32 +184,24 @@
         'run-test' : ['--pictest',
                       '--prebuild',
                       '--relocate',
-                      '--jit'],
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+                      '--jit']
     },
 
     # ART gtest configurations
     # (calls make 'target' which builds and then runs the gtests).
 
     'art-gtest' : {
-        'make' :  'test-art-host-gtest',
-        'env' : {
-            'ART_USE_READ_BARRIER' : 'true'
-        }
+        'make' :  'test-art-host-gtest'
     },
     'art-gtest-read-barrier': {
         'make' :  'test-art-host-gtest',
         'env' : {
-            'ART_USE_READ_BARRIER' : 'true',
             'ART_HEAP_POISONING' : 'true'
         }
     },
     'art-gtest-read-barrier-table-lookup': {
         'make' :  'test-art-host-gtest',
         'env': {
-            'ART_USE_READ_BARRIER' : 'true',
             'ART_READ_BARRIER_TYPE' : 'TABLELOOKUP',
             'ART_HEAP_POISONING' : 'true'
         }