DHT/Create : Failing to identify a linkto file in lookup_everywhere_cbk path

In case a file is not found in its cached subvol we proceed with
dht_lookup_everywhere. But as we dont add the linkto xattr to the
dictionary, we fail to identify any linkto file encountered.The
implication being we end up thinking the linkto file as a regular file
and proceed with the fop.

Change-Id: Iab02dc60e84bb1aeab49182f680c0631c33947e2
BUG: 1138389
Signed-off-by: Susant Palai <spalai@redhat.com>
Reviewed-on-master: http://review.gluster.org/8277
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-on: http://review.gluster.org/8602
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>