gossip: clarify what it means to 'discard a channel'

[niftynei]

It's unclear what it means to discard a channel. Instead,
let's use the common phrase to fail a channel.

I'm assuming that fail is the same as discard here, but maybe it's meant to say discard the message? (But that seems unlikely, given the context).

[TheBlueMatt]

This is in reference to channel_updates, not neccessarily our own channels. Failing would be appropriate if we were one of the sides of the channels, but as we are not, we cannot neccessarily "fail" the channel. You could clarify a bit further by saying something like "discard knowledge of the channel in its routing information".

[niftynei]

Thanks for the clarification. I updated the commit to just add a bit of clarifying text.

As you mention, what to do if this is one of your immediate peers isn't immediately clear from the spec. The htlc_maximum_msat is provided mainly as a guideline for route-finding nodes -- should your channel peers care that you're advertising weird data?

[Roasbeef]

How about ignore instead of discard?

[niftynei]

Works for me. Updated.