SUNRPC: rpcauth_create needs to know about rpc_clnt clone status

Ensure that we set rpc_clnt->cl_parent before calling rpc_client_register
so that rpcauth_create can find any existing RPCSEC_GSS caches for this
transport.

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