Merge git://git.linux-nfs.org/projects/trondmy/nfs-2.6

* git://git.linux-nfs.org/projects/trondmy/nfs-2.6:
  NFS: use correct fs type for v4 submounts and referrals
  Make nfs_file_cred more robust.
  NFS: Enable NFSv4 callback server to listen on AF_INET6 sockets