[TSan][libdispatch] Avoid infinite recursion in dispatch_apply[_f] interceptors

In libdispatch, dispatch_apply is implemented in terms of
dispatch_apply_f. Unfortunately, this means that we can't implement the
interceptor for dispatch_apply_f by forwarding to the dispatch_apply
interceptor.

In the interceptor dispatch_apply_f, we can't use WRAP(dispatch_apply).
WRAP(dispatch_apply) -> REAL(dispatch_apply_f). Requires duplication of
some setup code.

Reviewed By: kubamracek

Differential Revision: https://reviews.llvm.org/D59526

llvm-svn: 356467