Introduce a data server set_client and init session following the
nfs4_set_client and nfs4_init_session convention.
Once a new nfs_client is on the nfs_client_list, the nfs_client cl_cons_state
serializes access to creating an nfs_client struct with matching properties.
Use the new nfs_get_client() that initializes new clients.
Signed-off-by: Andy Adamson <andros@netapp.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>