glusterd/snapshot : Fail the snapshot create operation if geo-rep is running

As one of the recommandations for taking a snapshot is not to have
an active geo-replication session, its better to display an error
saying session is active when snapshot create command is issued.

Change-Id: I94593dbd2659610e033ca316176dda1ac8dc5ce6
BUG: 1145091
Signed-off-by: Sachin Pandit <spandit@redhat.com>
Reviewed-on: http://review.gluster.org/8461
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Rajesh Joseph <rjoseph@redhat.com>
Reviewed-by: Atin Mukherjee <amukherj@redhat.com>
Reviewed-by: Vijaikumar Mallikarjuna <vmallika@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Krishnan Parthasarathi <kparthas@redhat.com>
Signed-off-by: Sachin Pandit <spandit@redhat.com>
Reviewed-on: http://review.gluster.org/8804
cli/snapshot : update of a snapshot delete syntax in documentation.

Change-Id: Id1a4b9684a8dd5750ee6eed841e3d5195407fb7e
BUG: 1145084
Signed-off-by: Sachin Pandit <spandit@redhat.com>
Reviewed-on: http://review.gluster.org/8534
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Kaushal M <kaushal@redhat.com>
Signed-off-by: Sachin Pandit <spandit@redhat.com>
Reviewed-on: http://review.gluster.org/8805
Reviewed-by: Vijaikumar Mallikarjuna <vmallika@redhat.com>