Fix a bug in tf test runner

Atest will mistakenly always run tests with pretty output even though
the old output is enabled.

Test: m atest && ATEST_OLD_OUTPUT=1 atest-dev HelloWorldTests

Change-Id: Iae660ced73881ac84e4605556897bc5bb72ac4cf
diff --git a/atest/test_runners/atest_tf_test_runner.py b/atest/test_runners/atest_tf_test_runner.py
index 881b73a..0cbeb5d 100644
--- a/atest/test_runners/atest_tf_test_runner.py
+++ b/atest/test_runners/atest_tf_test_runner.py
@@ -257,7 +257,8 @@
             os.chdir(os.path.abspath(os.getenv(constants.ANDROID_BUILD_TOP)))
             if os.getenv(trb.OLD_OUTPUT_ENV_VAR):
                 result = self.run_tests_raw(test_infos, extra_args, reporter)
-            result = self.run_tests_pretty(test_infos, extra_args, reporter)
+            else:
+                result = self.run_tests_pretty(test_infos, extra_args, reporter)
         except atest_error.DryRunVerificationError as e:
             atest_utils.colorful_print(str(e), constants.RED)
             return ExitCode.VERIFY_FAILURE