cluster/dht: Added logging of new layout for dir-selfheal

Added a log which logs the new layout which will be used
for the directory self healing

It prints:

a) Subvolume name
b) Error --> Is needed because layout healing depends on
             the error and having it in log will help in
             debugging
c) Start     Starting of the layout range
d) Stop      Ending of the layout range

Change-Id: I48c9c697716a899165ed29b737362a75c62e09b3
BUG: 1113066
Signed-off-by: Venkatesh Somyajulu <vsomyaju@redhat.com>
Reviewed-on: http://review.gluster.org/8173
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>