feature/changelog: Change default rollover and fsync-interval time

  This will change the following default configurables.
   1. rollover-time: from 60 to 15.
   2. fsync-interval: from 0 to 5.

Change-Id: I9c8db01376967c4f19547ec87f54833f8b139d29
Signed-off-by: Kotresh H R <khiremat@redhat.com>
Reviewed-on: http://review.gluster.org/7545
Reviewed-by: Venky Shankar <vshankar@redhat.com>
Tested-by: Venky Shankar <vshankar@redhat.com>