NFS implement v4.0 callback_ident

Use the small id to pointer translator service to provide a unique callback
identifier per SETCLIENTID call used to identify the v4.0 callback service
associated with the clientid.

Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --cc fs/nfs/client.c
Simple merge

diff --cc fs/nfs/inode.c
Simple merge

diff --cc fs/nfs/internal.h
Simple merge

diff --cc fs/nfs/nfs4proc.c
Simple merge

diff --cc include/linux/nfs_fs_sb.h
Simple merge