tripleo.sh support updating and checking deployed overcloud
tripleo.sh support updating and checking deployed overcloud

Adds initial support for overcloud updates via the --overcloud-update option
which will update an already deployed overcloud heat stack.

Optionally we can check the before/after resources and prove that nothing
changed during the updates (no resources replaced, added or deleted) by
passing --enable-check.  In a future patch this will be enhanced to
allow for expecting specific changes, e.g via a regex or list.

Change-Id: Ie35360de617d0bbb1fa55c0f10956e6e669dda8d

openstack/tripleo-common,openstack/tripleo-common