webadmin: Fix vertical positioning of checkbox and label

Fixes vertical positioning of checkbox and its label if checkbox is
placed on the right of its label.

Change-Id: I38f8cf40fccfb0ec34672915f7aad15b2b08da75
Bug-Url: https://bugzilla.redhat.com/1148868
Signed-off-by: Martin Perina <mperina@redhat.com>