Add _create_overcloudrc_from_outputs
Add _create_overcloudrc_from_outputs

Refactors _create_overcloudrc into _create_overcloudrc_from_outputs such
that it can be used without requiring a stack.

Change-Id: I28c21f923baf75fbc3be501552c10a5bb5384a09
Signed-off-by: James Slagle <33ab48cedd1a7cf7a68e1b587db88f55f753652f@redhat.com>

openstack/tripleo-common,openstack/tripleo-common