cluster/afr: piggyback and fsync resume changes

1) pre_op_piggyback should always be decremented.
2) Move fsync resume to just after post_op.
3) fsync stub should be created from afr's local
   not from the final response.

Change-Id: I220bb532eb03bea584292f4dd2e816ad0c3e0cf7
BUG: 927146
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/4741
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>