nfs: Remove afr split-brain handling in nfs

We added this code as an interim fix until afr can
handle split-brains even when opens are not issued.
Afr code has matured to reject fd based fops when
there are split-brains so we can remove it.

Change-Id: Ib337f78eccee86469a5eaabed1a547a2cea2bdcf
BUG: 974972
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5227
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Ravishankar N <ravishankar@redhat.com>
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>