HAGrid quickstart warning about port

[madhavajay]

If someone runs quickstart on a server they might not be able to access the url without opening a port. We could check their external IP and then attempt to check the port if it responds we can show that URL if it does not, we can say running internally here:

✅ http://127.0.0.1:8888/token=xyz

Unable to access port 8888 on external interface you might need to open this. ❌ http://1.2.3.4:8888/token=xyz

It is a little hard to know what context a machine is running in but we could make an assumption that if the OS is Linux (or has no desktop) we do this check and if it isnt we ignore it?

I think interrogating $XDG_CURRENT_DESKTOP on linux and if not linux just ignoring this and assuming it's a "Desktop" situation.

https://unix.stackexchange.com/questions/116539/how-to-detect-the-desktop-environment-in-a-bash-script

[madhavajay]

I think this could extend to hagrid check where we could decide if should check for an external IP based off the same heuristic.