gluster: Corrected add brick event log message

Corrected the event log message for add brick case to "<No of bricks>
brick(s) added to volume <Volume name>".
Earlier it used to log the event as "<No of bricks> volume brick(s)
added to volume <volume name>".

Change-Id: I5930123ae042acf343d766cc81dd55567b50f27a
Bug-Url: https://bugzilla.redhat.com/987427
Signed-off-by: Shubhendu Tripathi <shtripat@redhat.com>