sunrpc: Remove TCP worker wrappers

The v4 and the v6 wrappers only pass the respective family
to the xs_tcp_setup_socket. This family can be taken from the
xprt's sockaddr.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>