cluster/afr: Handle parallel hardlinks self-heal

Change-Id: Ieda11870c65edae500140b6c061f15a7b3f264f3
BUG: 986905
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5370
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>