tests/cluster.rc: Moving the glusterd logs for cluster testcases

Moving the glusterd logs for cluster testcases from /d/backends to
logdir.

Change-Id: I6f22ca0c2faa87b0774e718c6c26d6547afd7c51
BUG: 1102593
Signed-off-by: Avra Sengupta <asengupt@redhat.com>
Reviewed-on: http://review.gluster.org/7924
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>