Adjust MIN_PORT to match other implementations

Adjust MIN_PORT to match other implementations

Port 33434 is the IANA-reserved port for traceroute. It also seems to be
the most common start port. The following implementations, and
likely others, use it as their start port:

- Apple macOS traceroute
- FreeBSD traceroute
- GNU inetutils-traceroute
- Modern traceroute for Linux
- OpenBSD traceroute

The benefit to using a standard starting port is that some firewalls may
have these ports allowed, whereas other ports may be blocked, so there
is a greater probability the probe will succeed.