Make sure any config overrides are reset
Make sure any config overrides are reset

The new deploy unit tests have conf.set_override() but
don't reset these after each test, so depending on the
test order there are failures.

This just addes a generic cleanup in the base class to catch
all of them.

Change-Id: Idb1b4ef158808b08657f34bfe1546fa2ec0dae9f

openstack/kolla-mesos,openstack/kolla-mesos,openstack/kolla-mesos,asalkeld/kolla-mesos