gluster/uss: Handle ESTALE in snapview client  when NFS server restarted

When NFS server is restarted inode-context is lost.
Nameless lookup will be sent to regular volume.
If the gfid is from virtual graph, lookup will fail
with ESTALE. We need to send a lookup to snapview server

Change-Id: I22920614f0d14cb90b53653fce95b6b70023eba6
BUG: 1166197
Signed-off-by: vmallika <vmallika@redhat.com>
Reviewed-on: http://review.gluster.org/9153
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Sachin Pandit <spandit@redhat.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>