cluster/dht: Make sure loc has gfid

Problem:
In some code paths neither loc->gfid nor loc->inode->gfid
is populated which leads to EINVAL for linkfile setattr
in dht_linkfile_attr_heal.

Fix:
Populate loc->gfid before dht_linkfile_attr_heal.

Change-Id: I062770e6f6eaead304eff1dae81f8588a3b97eed
BUG: 971805
Signed-off-by: Pranith Kumar K <pkarampu@redhat.com>
Reviewed-on: http://review.gluster.org/5178
Reviewed-by: Shishir Gowda <sgowda@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>