cluster/afr: Have common inode-write-fop cbk

Change-Id: Ia7b324b86d6a7051d187106d7a060155e77defc5
BUG: 910217
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5238
Reviewed-by: Ravishankar N <ravishankar@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>