gsyncd / geo-rep: maximum number of retries per changelog

With entry retries MAX_RETRIES is the threashold for the number
of times we retry a changelog. After hitting this limit, the
changelog is marked as processed after warning for incompleteness
in the log.

Change-Id: I777b71b4cdaa63335d9c936f2d64e5c0264a0f26
BUG: 1003803
Signed-off-by: Venky Shankar <vshankar@redhat.com>
Reviewed-by: Amar Tumballi <amarts@redhat.com>
Tested-by: Amar Tumballi <amarts@redhat.com>
Reviewed-on: http://review.gluster.org/5758
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Avra Sengupta <asengupt@redhat.com>
Tested-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-by: Anand Avati <avati@redhat.com>