webadmin: clone vm from snapshot - validate disk sd

Clone VM from Snapshot:
verify that a target storage domain is selected for each disk.

Change-Id: I1f5148295b46ce4394c407881217d34d3f7443a8
Related-To-Bug-Url: https://bugzilla.redhat.com/975114
Signed-off-by: Daniel Erez <derez@redhat.com>