Thread safety analysis: Add note for unlock kind mismatch

Summary:
Similar to D56967, we add the existing diag::note_locked_here to tell
the user where we saw the locking that isn't matched correctly.

Reviewers: aaron.ballman, delesley

Reviewed By: aaron.ballman

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D59455

llvm-svn: 356427