core: Change disks status to illegal.

Event log is reporting changing disk status to illegal but disks stay
in locked state
The proposed fix is to change the disks statuses to ILLEGAL and log
which disks were not at ILLEGAL state in the first place to make it easy
to resolve bugs.

Change-Id: Ic4075c03b8d70d50b69222c73169ccc63e3ab66e
Related-to: https://bugzilla.redhat.com/880687
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>