ipsec tests newly failing after pcap update

[Taylor R Campbell <campbell+netbsd-tech-net%mumble.net@localhost>]

About ten ipsec tests have started failing since the libpcap update:

https://releng.netbsd.org/b5reports/i386/commits-2023.08.html#build-2023.08.19.14.22.41

They all look similar -- `ipip-proto-4' is no longer appearing in
output of `tcpdump -n -e -r ...'.  Here's an example:

Fail: regexp 20.0.0.1 > 20.0.0.2: 10.0.1.2 > 10.0.2.2: ICMP echo request, .+ \(ipip-proto-4\) not in stdout

00:00:01.470004 b2:a0:30:b8:83:e8 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Request who-has 20.0.0.2 tell 20.0.0.1, length 28
00:00:01.420004 b2:a0:fe:9e:77:6d > b2:a0:30:b8:83:e8, ethertype ARP (0x0806), length 42: Reply 20.0.0.2 is-at b2:a0:fe:9e:77:6d, length 28
00:00:01.470004 b2:a0:30:b8:83:e8 > b2:a0:fe:9e:77:6d, ethertype IPv4 (0x0800), length 118: 20.0.0.1 > 20.0.0.2: 10.0.1.2 > 10.0.2.2: ICMP echo request, id 47271, seq 0, length 64
00:00:01.420004 b2:a0:fe:9e:77:6d > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 42: Request who-has 20.0.0.1 tell 20.0.0.2, length 28
00:00:01.470004 b2:a0:30:b8:83:e8 > b2:a0:fe:9e:77:6d, ethertype ARP (0x0806), length 42: Reply 20.0.0.1 is-at b2:a0:30:b8:83:e8, length 28
00:00:01.420004 b2:a0:fe:9e:77:6d > b2:a0:30:b8:83:e8, ethertype IPv4 (0x0800), length 118: 20.0.0.2 > 20.0.0.1: 10.0.2.2 > 10.0.1.2: ICMP echo reply, id 47271, seq 0, length 64

Can someone take a look?