[powerpc] deactivate flakey test halt_on_error-torture.cc on powerpc64 be

This test case occassionally fails when run on powerpc64 be.

asan/TestCases/Posix/halt_on_error-torture.cc

The failure causes false problem reports to be sent to developers whose
code had nothing to do with the failures.  Reactivate it when the real
problem is fixed.

This could also be related to the same problems as with the tests
ThreadedOneSizeMallocStressTest, ThreadedMallocStressTest, ManyThreadsTest,
and several others that do not run reliably on powerpc.

llvm-svn: 303864