Mark ESX driver as deprecated

Since the ESX and VC drivers actually share a lot of code, we could
keep the ESX driver.  However, after speaking with some of the VMware
team, the driver could be simplified a good bit if we just drop ESX
support since there is no intention to support it in its current form.

Instead of just pulling it now (based on the hypervisor deprecation
plan that required CI), we'll mark it deprecated for Icehouse and pull
it out for Juno.

DocImpact

Change-Id: I6553e8b39610cae78e5561e8d03a919476f0d99f
Move libvirt RBD utilities to a new file

This will make it easier to share rbd-related code with
cinder and glance. Port the applicable unit tests over
from cinder.

Change-Id: I5bf08da87daf1d98f326f21cf33aba68aa830785
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Merge "Move libvirt RBD utilities to a new file"
Merge "Mark ESX driver as deprecated"