[DCCP]: dccp_v(4|6)_ctl_socket is leaked.

This seems a purism as module can't be unloaded, but though if cleanup
method is present it should be correct and clean all staff created.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>