uss/gluster: Move all uss related logs into subfolder

For USS we have 1 snapd log per volume and as many snap logs for volume.
For example if there are 4 volumes having 256 snaps each and USS is
enabled than total number of logs under /var/log/glusterfs for USS would
be 1028 logs.

Total logs = (4(snapd per volume) + 4(volumes)*256(snaps)) = 1028

Hence, it makes sense to move into into sub-folder structure like

/var/log/glusterfs/snaps/<vol-name>/<snapd + snaps logs>

Change-Id: I29262e6458c3906916923cd67d1145d6ae10bec3
BUG: 1160534
Signed-off-by: vmallika <vmallika@redhat.com>
Reviewed-on: http://review.gluster.org/9050
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Rajesh Joseph <rjoseph@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Krishnan Parthasarathi <kparthas@redhat.com>