Fix expectedFailureLLGS to expect failure when host platform is not linux.

Fix expectedFailureLLGS to expect failure when host platform is not linux.

expectedFailureLLGS has an early return false if the platform is not linux
except it should be checking the target platform on which the server is
running for remote tests.

Test Plan:
Verify expected failure when running from mac to remote linux llgs:
TestBreakAfterJoin.py, TestCreateDuringStep.py, TestExitDuringBreak.py,
TestProcessLaunch.py, TestThreadStates.py

Differential Revision: http://reviews.llvm.org/D8869

llvm-svn: 234492