Expand gluster's NFS FD header to 4 bytes

* https://bugzilla.redhat.com/show_bug.cgi?id=950121
* Oracle's DNFS does not properly XDR encoding on NFS FDs that
  are not congruent to 0mod4 bytes long
* This patch is a workaround to support Oracle's buggy code

Change-Id: Ic621e2cd679a86aa9a06ed9ca684925e1e0ec43f
BUG: 950121
Signed-off-by: Michael Brown <michael@netdirect.ca>
Reviewed-on: http://review.gluster.org/4918
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>