Clean up: Code that takes and releases nfs_client_lock remains in
nfs_get_client(). Logic that handles a pre-existing nfs_client is
moved to a separate function.
No behavior change is expected.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>