Enable algorithm net tests for 3.18 kernels

With the backport of 00bc0ef, 3.18 kernels no longer hang on the
xfrm algorithm tests. This patch re-enables these tests for all 3.18
kernels.

Bug: 63589559
Test: All kernel tests run, passing.
Change-Id: I27b7e463a5566b1211ef6248f9239a52ff39d50d
diff --git a/net/test/xfrm_algorithm_test.py b/net/test/xfrm_algorithm_test.py
index 1de6e4b..6adc461 100755
--- a/net/test/xfrm_algorithm_test.py
+++ b/net/test/xfrm_algorithm_test.py
@@ -136,7 +136,6 @@
     new_name = new_name.replace("(", "-").replace(")", "")  # remove parens
     setattr(cls, new_name, TestClosure)
 
-  @unittest.skipIf(net_test.LINUX_VERSION[:2] == (3, 18), "b/63589559")
   def ParamTestSocketPolicySimple(self, params):
     """Test two-way traffic using transport mode and socket policies."""