fixed spinner for wizard secure dialog

currently on the last wizard step after form
submitted we may see just a spinner without
background. This change is fixing it.

Change-Id: Ia93b71eb38f4105d32bf7a2cee97110ca765a6e4
Reviewed-on: http://review.couchbase.org/40382
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>