Get rid of checking for ip sec history. It is true that packets are not

supposed to be checked by the firewall rules twice. However, because the
various ipsec handlers never call ip_input(), this never happens anyway.

This fixes the situation where a gif tunnel is encrypted with IPsec. In
such a case, after IPsec processing, the unencrypted contents from the
GIF tunnel are fed back to the ipintrq and subsequently handeld by
ip_input(). Yet, since there still is IPSec history attached, the
packets coming out from the gif device are never fed into the filtering
code.
This fix was sent to Itojun, and he pointed towartds
    http://www.netbsd.org/Documentation/network/ipsec/#ipf-interaction.
This patch actually implements what is stated there (specifically:
Packet came from tunnel devices (gif(4) and ipip(4)) will still
go through ipf(4). You may need to identify these packets by
using interface name directive in ipf.conf(5).

Reviewed by:	rwatson
MFC after:	3 weeks

sys/netinet/ip_input.c

@@ -421,11 +421,6 @@ ip_input(struct mbuf *m)
 			m_adj(m, ip->ip_len - m->m_pkthdr.len);
 	}
 
-#ifdef IPSEC
-	if (ipsec_gethist(m, NULL))
-		goto pass;
-#endif
-
 	/*
 	 * IpHack's section.
 	 * Right now when no processing on packet has done