tests/bug-961307.t: echo output string in case of failure for easy debug.

Change-Id: I5bb5d7f2d9380da3247588e8eff10b559e17ff3f
BUG: 1122533
Signed-off-by: Kotresh H R <khiremat@redhat.com>
Reviewed-on: http://review.gluster.org/8362
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>