feautre/gfid-access: Fix EINVAL when stat on .gfid

Problem: Some of the inode operations on '.gfid'
virtual directory was resulting in the error
EINVAL from dht after failing to find the layout.

Solution: Inode operations on '.gfid' virtual directory
should not wind further down and should be handled
accordingly in the gfid-access translator itself.

Change-Id: I156cb10ffea0c46b0d747e26f74538d7fb01a1dd
BUG: 1105891
Signed-off-by: Kotresh H R <khiremat@redhat.com>
Reviewed-on: http://review.gluster.org/8011
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Raghavendra G <rgowdapp@redhat.com>
Reviewed-by: Venky Shankar <vshankar@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/8234
Reviewed-by: Niels de Vos <ndevos@redhat.com>