Update .coveragerc after the removal of openstack directory
Update .coveragerc after the removal of openstack directory

The openstack directory was used to keep codes from oslo-incubator,
we have retired oslo-incubator,so don't use this directory any more.

Change-Id: I846087668e5291521632e941250b0df4a1b87521

openstack/dragonflow,openstack/dragonflow,openstack/dragonflow