[sanitizer] a bit more informative deadlock detector report (still lots to improve)

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@204115 91177308-0d34-0410-b5e6-96231b3b80d8
tsan: fix flaky test



git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@204119 91177308-0d34-0410-b5e6-96231b3b80d8