Updated openstack/openstack
Project: openstack/oslo.middleware  72836d0126483b60dd6eb7687cdf38eecec969f9

Fix coverage testing

Add coverage to test-requirements so that tox-e cover works - this
is part of the post jobs that are run.

Change-Id: Id919bdb861447c0f018df64d9a0f5e44c0cc2351