thread state coordinator: fixed bug in thread running state book-keeping.

Adds a test to verify that a thread resume request marks the thread as running
after doing the resume callback.  This test fails without the corresponding
ThreadStateCoordinator.cpp change.

Fixes the code where that state was not maintained.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@219412 91177308-0d34-0410-b5e6-96231b3b80d8