cluster/dht: Changed log level to DEBUG

Change-Id: Ia4dde95367b44d63f57f0840c2a2f351b1cfb072
BUG: 1138602
Signed-off-by: Venkatesh Somyajulu <vsomyaju@redhat.com>
Reviewed-on: http://review.gluster.org/8697
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>