Revert r374006: Reland 'Add VFS support for sanitizers' blacklist'

Also revert follow-up changes to the test.
Reason: the patch breaks our internal clang-tidy integration.

It's also unclear why we should use getRealPath instead of plumbing the
VFS to SanitizerBlacklist, see original commit thread of cfe-commits for
a discussion.

llvm-svn: 374151