Now that we have clustered services it is no longer correct to refer to
"hosts" in the scheduler, as we may be referring to a cluster sometimes.
This patch changes those cases where "host" is no longer appropriate
(ie: `find_retype_host`) and uses the more generic name "backend" (ie:
`find_retype_backend`).
Specs: https://review.openstack.org/327283
Implements: blueprint cinder-volume-active-active-support
Change-Id: I6edbdaf5f38841c7e801b5f3fc0cab3e8ef44a20
Gorka Eguileor
41bbdbc8a9