If rbd is used for glance, but compute is using local ephemeral storage,
nova-compute can direct download the images in this scenario from the
glance ceph pool via rbd, instead going through glance api.
This change introduce new compute role based parameters to enable direct
download of glance images via rbd. If NovaGlanceEnableRbdDownload is set,
per default the global RBD glance parameters are used, CephClientUserName
GlanceRbdPoolName and CephClusterName for the used ceph.conf.
Glance also support multi storage backends which can be configured using
GlanceMultistoreConfig. If additional RBD glance backends are configured,
the NovaGlanceRbdDownloadMultistoreID can be used to pointing to the
hash key (backend ID) of GlanceMultistoreConfig to use.
Depends-On: https://review.opendev.org/c/openstack/puppet-tripleo/+/772168
Depends-On: https://review.opendev.org/c/openstack/puppet-nova/+/770687
Change-Id: I020da468d909bd98819f1e3618bf905260791d9b
91837d4fa7