ping tests: Add tests for IP header options

The function pr_pack() prints out a packet, if the IP packet contains
options, these are printed as well.

Test the functionality fixed in
70960bb86a3ba5b6f5c4652e613e6313a7ed1ac1.

Reviewed by: markj
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D38470