core: Check live snapshot capabilities in live storage migration CDA

Change-Id: Idba6581587d1908e4428ea2d18878c2f62a0b317
Bug-Url: https://bugzilla.redhat.com/1158049
Bug-Url: https://bugzilla.redhat.com/1105846
Signed-off-by: Tal Nisan <tnisan@redhat.com>