core: Add space validation when creating snapshot

In CreateAllSnapshotsFromVmCommand, added to CDA missing storage space validations.
For that, added allDomainsHaveSpaceForNewDisks to
MultipleStorageDomainsValidator .

Added relevant tests.

Change-Id: I0a5b5df695d30a34fbdef31da2320b322e27466b
Bug-Url: https://bugzilla.redhat.com/1053752
Signed-off-by: Vered Volansky <vvolansk@redhat.com>