core: Empty Change CD List when ISO is Inactive

The VM's Change CD list should be empty when the ISO domain in the DC is
inactive.

Change-Id: I784be2510e2f51be277f7ee06a5bd5573ab23d66
Bug-Url: https://bugzilla.redhat.com/1085398
Signed-off-by: Idan Shaby <ishaby@redhat.com>