Disable regrtest timeout until #11753 and #11755 are fixed

The traceback may contain "_is_owned":

Thread 0x40962b90:
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 220 in _is_owned
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 227 in wait
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 421 in wait
  File "<string>", line 23 in run
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 735 in _bootstrap_inner
  File "/srv/buildbot/buildarea/3.x.bolen-ubuntu/build/Lib/threading.py", line 708 in _bootstrap

Current thread XXX:
  File "<string>", line 10 in dump
  File "<string>", line 28 in <module>

file-like objects using a new `fileobj` constructor argument.  Patch by
Nadeem Vawda.

 * faulthandler_user() displays the tracebacks of all threads even if it is
   unable to get the state of the current thread
 * test_faulthandler: only release the GIL in test_gil_released() check
 * create check_signum() subfunction

 * faulthandler_cancel_dump_tracebacks_later() is responsible to set running
   to zero (so we don't need the volatile keyword anymore)
 * release locks if PyThread_start_new_thread() fails

assert(thread.running == 0) was wrong in a corner case

Always release the cancel join.

Fix also another corner case: _PyFaulthandler_Fini() called after setting
running variable to zero, but before releasing the join lock.

If the thread releases the join lock before the cancel lock, the thread may
sometimes still be alive at cancel_dump_tracebacks_later() exit. So the cancel
lock may be destroyed while the thread is still alive, whereas the thread will
try to release the cancel lock, which just crash.

Another minor fix: the thread doesn't release the cancel lock if it didn't
acquire it.

The split probably won't happen for a while, but I might as well lay the
groundwork now since I'll be adding new test modules before too long.