Re-enable TestExprDoesntBlock.py on Linux.

This is related to:
http://llvm.org/bugs/show_bug.cgi?id=15258

I ran this test 10 times successfully against Ubuntu 12.04 LTS x86_64
with lldb built with gcc 4.8.2 and July 2013 libedit.

llvm-svn: 202456

lldb/test/functionalities/expr-doesnt-deadlock/TestExprDoesntBlock.py

@@ -24,7 +24,7 @@ class ExprDoesntDeadlockTestCase(TestBase):
 
     @dwarf_test
     @expectedFailureFreeBSD('llvm.org/pr17946')
-    @skipIfLinux # llvm.org/pr15258: disabled due to assertion failure in ProcessMonitor::GetCrashReasonForSIGSEGV:
+    # @skipIfLinux # llvm.org/pr15258: disabled due to assertion failure in ProcessMonitor::GetCrashReasonForSIGSEGV:
     def test_with_dwarf_and_run_command(self):
         """Test that expr will time out and allow other threads to run if it blocks."""
         self.buildDwarf()