[NETFILTER/RXRPC]: Don't use seq_release_private where inappropriate.

Some netfilter code and rxrpc one use seq_open() to open
a proc file, but seq_release_private to release one.

This is harmless, but ambiguous.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>