Deploy overcloud images from seed

There are some use cases where deploying the overcloud from the
undercloud is not necessary. Using --no-undercloud we can deploy the
overcloud using the heat from seed.

Change-Id: I7fe3b7957c93f3ebb0796a7e7796fcb2328e07d2
Co-Authored-By: Robert Collins <rbtcollins@hp.com>
Merge "Deploy overcloud images from seed"