Do not leak THR_FLAGS_SUSPENDED from the previous suspend/resume
cycle. The flag currently is cleared by the resumed thread. If next
suspend request comes before the thread was able to clean the flag, in
which case suspender skip the thread.
Instead, clear the THR_FLAGS_SUSPEND flag in resume_common(), we do
not care how much code was executed in the resumed thread when the
pthread_resume_*np(s) functions returned.
Reported by: Lawrence Esswood <firstname.lastname@example.org>
MFC after: 1 week