mgmt/glusterd: display snapd status as part of volume status

* Made changes to save the port used by snapd in the info file for the volume
  i.e. <glusterd-working-directory>/vols/<volname>/info

This is how the gluster volume status of a volume would look like for which the
uss feature is enabled.

[root@tatooine ~]# gluster volume status vol
Status of volume: vol
Gluster process                                         Port    Online  Pid
------------------------------------------------------------------------------
Brick tatooine:/export1/vol                             49155   Y       5041
Snapshot Daemon on localhost                            49156   Y       5080
NFS Server on localhost                                 2049    Y       5087

Task Status of Volume vol
------------------------------------------------------------------------------
There are no active volume tasks

Change-Id: I8f3e5d7d764a728497c2a5279a07486317bd7c6d
BUG: 1111041
Signed-off-by: Raghavendra Bhat <raghavendra@redhat.com>
Reviewed-on: http://review.gluster.org/8114
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>