BUG/MEDIUM: thread: check stopping thread against local bit and not global one

Commit ef422ced9 ("MEDIUM: thread: make stopping_threads per-group and add
stopping_tgroups") moved the stopping_threads mask to per-group, but one
test in the loop preserved its global value instead, resulting in stopping
threads never sleeping on stop and eating 100% CPU until all were stopped.

No backport is needed.
1 file changed