glusterd: Made log-rotate use synctask framework.

Change-Id: Ib305168759db6730dfa0045da99de252eb5e9469
BUG: 852147
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/4478
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Reviewed-by: Anand Avati <avati@redhat.com>