engine: StorageVersionUtil fixes

Implemented several fixes:
* Do not fail attaching a domain if the storage format is too high
  (As was present before change-id
  I47fb8b14e5c97b601c8fc0cc296a4ec42a48227a).
* Don't force unneeded upgrades

Also add a distinction between block and file domain for V2.

Change-Id: Iaf7eb690f343b1cf8007a9d8b30a3ce22a6a57dc
Related-To: https://bugzilla.redhat.com/show_bug.cgi?id=950023
Signed-off-by: Allon Mureinik <amureini@redhat.com>
frontend: display correct format in edit domain

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=950023
Change-Id: I0432d633fabcf62b14b267b8dd9ca517b69c029a
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>