webadmin: Show spanner icon when storages are in maintanance

When a storage is in maintanance show a spanner icon in the storage data
center sub tab and in the storage main tab.
As an added bonus this patch also fixes a bug that shows locked data
centers as inactive in the storage main tab

Change-Id: Ied36b2534ce321fe7ee5efde8bc1fc9cb1d70c0b
Signed-off-by: Tal Nisan <tnisan@redhat.com>
Bug-url: https://bugzilla.redhat.com/1004153