mgmt/glusterd, socket: Change logging for brick disconnects

For unix path based sockets, the socket path is
cryptic (md5sum of path) and may not be useful for
the user in debugging so log it in DEBUG.

Changed logging in brick_rpc_notify to log brickinfo
for disconnects.

Change-Id: I69174bbbbde8352d38837723e950ad8fc15232aa
BUG: 963153
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5009
Reviewed-by: Niels de Vos <ndevos@redhat.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>