Modify how overcloud image with patched repository is updated.
Modify how overcloud image with patched repository is updated.

Currently overcloud image is being updated with custom packages
together with system packages. This change modifies to first update
all packages within overcloud image and then update with packages
from custom repository.

This change is required to address rhbz#1655542

Change-Id: I6958c11f8104a92d4816f18b399ebc8dc983ef1f

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared