cluster/afr: wakeup delayed post op on fsync

Change-Id: I5d84ef72615f9d71b4af210976e2449de6e02326
BUG: 888174
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/4446
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>