[powerpc] deactivate tests combined.test and object.test on powerpc64 be

These tests fail on powerpc64 BE (only, not LE) and are thus intefering with
the running of 3 of the powerpc buildbots.  The author of the tests has been
notified and is working on fixing them but in the meantime I am disabling
them to get the bots working again.

See https://bugs.llvm.org//show_bug.cgi?id=33429

llvm-svn: 305317