core: check storage domains status on master deactivation

When deactivating the master storage domain we should make sure that the
other domains are not in transition.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1128824
Change-Id: I28228f2ad3ce555aafc9ea03d44aebeb12bbf0cf
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>