monkey patch stdlib before importing other modules

monkey patch stdlib before importing other modules

Some oslo libraries assume that stdlib is already patched when
they are imported (e.g. oslo_concurrency.processutils tests the
'time' module for monkey_patching to detect which 'subprocess'
module to import.

This can cause issues when things like test frameworks import
modules that monkey_patch, as the order imports are made can break
this kind of check. It is always good to monkey patch as soon as
possible, hence trying to do the patching in neutron/__init__.py.

This is an alternative to https://review.openstack.org/#/c/153225/
which just patches neutron/tests/__init__.py. Unfortunately, just
monkey_patching in tests/__init__.py didn't fix all of the issues
I ran into. For example, tempest tests were failing with timeouts.

Closes-bug: #1418541
Change-Id: I7f2115a99acae5b6d61aab2f7334f498b8d99858