[2.7] bpo-21149: Workaround a GC finalization bug in logging. (#4368)

[2.7] bpo-21149: Workaround a GC finalization bug in logging. (#4368)

* Work around a GC process finalization bug.

The logging RLock instances may exist but the threading.RLock class
itself has already been emptied causing a
Exception TypeError: "'NoneType' object is not callable" in <function _removeHandlerRef ..."
to be printed to stderr on process termination.

This catches that exception and ignores it because there is absolutely
nothing we can or should do about it from the context of a weakref
handler called from the gc context.