Switch to scapy with python 3.

Use consistent address schema with local and remote machine. Fill
variables with example IPs from my daily test run.

Do not use privileged or NFS source ports for UDP packets as inetd
ignores such packets. This should avoid some sporadic failures.
While there, use variable names consistently in all tests.

Put all make targets in a loop and print a little more what each
IPv6 fragment header test is doing.

Send fragment with Hop-by-Hop extension header after the fragment
header. I must not be processed.