Add support for creating heat stack domain

The Heat instance-users blueprint requires an additional domain
where heat creates projects and users related to stack resources
so add support for creating this domain when configured to install
Heat.  Note a workaround is currently required to make the
openstack command work with the v3 keystone API.

Change-Id: I36157372d85b577952b55481ca5cc42146011a54
Merge "Add support for creating heat stack domain"