[asan] Relax stack-overflow test.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@201571 91177308-0d34-0410-b5e6-96231b3b80d8
[sanitizer] make sure the deadlock detector survives the change of epochs; add a test and a comment

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@201572 91177308-0d34-0410-b5e6-96231b3b80d8