Glusterd/Remove-brick: Reconfigure the nfs server volfile upon remove-brick start

Problem : For remove-brick start operation  all client volfiles are reconfigured
except nfs server volfile. Hence, even after layout is fixed by the rebalance
process, the nfs clients dont see the change and go on creating directories and
files in the decommissioned brick which leads to data loss after remove-brick
commit.

Solution : Reconfigure the nfs server volfile for remove-brick start

credit: kaushal@redhat.com
        spalai@redhat.com

Change-Id: Ib8cd8b45a9e1f888d5e00dff65cdf77c1613a2af
BUG: 1070734
Signed-off-by: Susant Palai <spalai@redhat.com>
Reviewed-on: http://review.gluster.org/7162
Reviewed-by: Kaushal M <kaushal@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>