[autopilot-manager] Note on mavlink-routerd behavior

I'm creating this issue so we are aware, alongside with #3433, of this other behavior difference to mavlink-server:

Our TCP server endpoint at `127.0.0.1:5777`, when using mavlink-routerd, is accessible from any network, effectively acting as `0.0.0.0:5777`.

This differs from mavlink-server, which honors the `127.0.0.1`, prohibiting any connection from other networks. Note that any container that is not using host's network (`--net=host`), like usual extensions, won't be able to connect to it, since Docker has its own network.

This is probably another caveat to keep in your notes, @ES-Alexander.