Configure glance_host on the volume node (cinder)

If the glance_host option is not set in the volume node configuration,
cinder will not be able to create bootable volumes from images
(cinder-volume assumes that glance runs locally).

Also add <replaceable> markup on a couple 'controller' values.

Change-Id: I3aea0344813f46e012c40e081e6c513c979b32b9
Merge "Configure glance_host on the volume node (cinder)"