engine: Fixed ChangeCD dialog on inactive ISO domain

ChangeCD dialog no longer displays blank line which upon selection caused
NullPointerException.

Now the only available option when the ISO domain is
unavailable is 'Eject'.

Change-Id: I257e5f5fcfec0ab5c24dfaefa5c7f9330079141b
Bug-Url:https://bugzilla.redhat.com/show_bug.cgi?id=907506
Signed-off-by: Martin Betak <mbetak@redhat.com>