core: Fix faulty CDA in AddVmAndCloneImageCommand

In case super returned true, CDA returned true with no regard to what
happens in the for loop. This patch aims to implement to author's
original intention while using early return.

Change-Id: Ib4e63bf719a9bc98145a6401b05ed47005655486
Signed-off-by: Vered Volansky <vvolansk@redhat.com>
engine: Exclude read-only disks when creating a snapshot

Change-Id: Ib05f61e5a61616908bd31aa0fc3ee3e477655e67
Bug-Url: https://bugzilla.redhat.com/1056169
Signed-off-by: Sergey Gotliv <sgotliv@redhat.com>