Fix creation of share from snapshot

Current behaviour does not take into accout source host of snapshot for
share creation from snapshot. It leads to impossibility to create share
if improper host was scheduled using multibackend setup.

Solution:
Implement config opt that allows us call required host directly without
scheduling in case we have host restriction and allow scheduling in case
we don't. We do not have such restricion, for example, using multibackend
installation with generic drivers onboard.

Change-Id: I0743c92b55e123409133ea623e0f8ec03d8e9aaa
Closes-Bug: #1373882
Merge "Fix creation of share from snapshot"