Update from oslo incubator

Details about this change:
* Cleaned up openstack-common.conf, this file should contain
  only direct dependencies of Murano
* Removed unused files from openstack/common
* Moved xmlutils to murano/common; this module was removed from
  oslo-incubator long time ago, but is still used by
  common/wsgi.py, which also was deprecated by Oslo and adopted
  by Murano

Change-Id: I118de30bb0bae577d24d86fa723522580beb13d0
Merge "Update from oslo incubator"