cli : Maintain separate cli log file per cli instance for cluster regression tests

Change-Id: I7f49f4999d997b99c103fd67d13f972937e3aa92
BUG: 1162987
Signed-off-by: Atin Mukherjee <amukherj@redhat.com>
Reviewed-on: http://review.gluster.org/9100
Reviewed-by: Kaushal M <kaushal@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Krishnan Parthasarathi <kparthas@redhat.com>