cluster/afr: Eliminate locking in sh domain in metadata self-heal

Change-Id: I9ef25a17c9a43ba06fac2ad3f7c18cb47de91537
BUG: 1170913
Signed-off-by: Krutika Dhananjay <kdhananj@redhat.com>
Reviewed-on: http://review.gluster.org/9240
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Pranith Kumar Karampuri <pkarampu@redhat.com>
Tested-by: Pranith Kumar Karampuri <pkarampu@redhat.com>