[all] oslotest 4.0 drops the moxstubout and functional modules, stestr dependency

Per $subject, the 'oslotest.moxstubout' modules has been removed in oslotest 4.0 and we no longer include 'stestr' in our list of dependencies. I think I've resolved all issues in the 'openstack/' namespaced projects, but if not the remedies are to either switch to mock or explicitly included 'stestr' in your 'test-requirements.txt' file, respectively. We've also removed the 'oslotest.functional' module, but there do not appear to have been any users of this module. Stephen