glusterd/snapshot : Copy the quota config and cksum file before taking a snapshot

Quota config and cksum file needs to be copied before taking a
snapshot, so that when a snapshot is restored these files is
copied back to the original place, and the restored snap volume
can make use of these quota files.

Before taking a snapshot the quota files are copied to
/var/lib/glusterd/snaps/<snapname>/quota/

Change-Id: Id175f28d4ee47be64d7491c6aae81a1794928490
BUG: 1061685
Signed-off-by: Sachin Pandit <spandit@redhat.com>
Reviewed-on: http://review.gluster.org/7527
Reviewed-by: Vijaikumar Mallikarjuna <vmallika@redhat.com>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Reviewed-by: Rajesh Joseph <rjoseph@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>