ping tests: Add a regression test
Test regression fixed in 4630a3252ac8. Add two tests that do not
use the verbose flag, so the code path in question can be reached:
- Respond with a proper ICMP destination host unreachable packet.
- Respond with a doctored ICMP destination host unreachable packet, that has the ICMP Identifier field modified (+1 bit).
Reviewed by: cy
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D39244