[tsan] Fix detached threads in unit tests on OS X

We need to call the intercepted version of pthread_detach. Secondly, PTHREAD_CREATE_JOINABLE and PTHREAD_CREATE_DETACHED are not 0 and 1 on OS X, so we need to properly pass these constants and not just a bool.

Differential Revision: http://reviews.llvm.org/D14837

llvm-svn: 253775