[hwasan] Fix TestCases/thread-uaf.c.

On newer glibc, this test detects an extra match somewhere under
pthread_getattr_np. This results in Thread: lines getting spread out in
the report and failing to match the CHECKs.

Fix the CHECKs to allow this possibility.

Reviewed By: fmayer

Differential Revision: https://reviews.llvm.org/D111841