webadmin: Renaming Add Brick UI action to Add

renamed the UI Action 'Add Bricks' in Bricks sub tab to just 'Add' for
UI consitency.

Change-Id: Iba0e7f9752893df37fa848b76a7698e3af139bc9
Bug-Url:://bugzilla.redhat.com/show_bug.cgi?id=1019568
Signed-off-by: Ramesh Nachimuthu <rnachimu@redhat.com>