Feature/public visors advertising

[i-hate-nicknames]

Did you run make format && make check?

Fixes #574

Changes:

On start visor registers itself in the service discovery. Visor attaches IPs of its local active network interface to the request;
If public_autoconnect field is set to true in config, visor will try to connect to 5 known visors on its start.

[i-hate-nicknames]

One thing I dislike is that I had to rely on callbacks in autoconnect. This is due to the reason that autoconnect needs transport manager, but importing transport manager introduces dependency cycle: transport package depends on servicedisc package.

I'm thinking about restructuring it a better way, maybe splitting some packages. Input on this subject is welcome.

[ersonp]

@i-hate-nicknames I was testing out the PR and skywire-cli visor gen-config generates config for v1.1.0 and not for v1.1.1.

[i-hate-nicknames]

Weird, I just checked and it generated 1.1.1 for me. Is it possible that you didn't build with make build and accidentally ran an old binary?

[ersonp]

make build; make install solved it. And connect_to_public_visors mentioned above. I could not find it in the config. Perhaps you meant public_autoconnect.

[jdknives]

Overall good work although some of the implementation details might be improvable.

[alexadhy]

Awesome code, lgtm.