bridge: consider what to do with superuser: try on "init" state for superuser bridge

[allisonkarlitskaya]

If someone requests a channel with superuser: "try" and we're in the init state for the superuser bridge, we'll queue the message waiting for the authentication to succeed. If it fails, we drop the message on the floor, closing the channel. There are three things we could do here:

• try to redeliver the message (hard)
• don't queue "try" messages on pending superuser bridges — handle them in the unprivileged bridge (easy)
• keep doing what we do now

We should look at what the C bridge did there.

cc @jelle @mvollmer

[allisonkarlitskaya]

Option 4 after discussing this on IRC a bit: we can do a hard reload of pages for the case where we de-authenticate. This would prevent anyone from ever having to worry about channels closing due to the superuser bridge stopping.

The next logical extension of this: hard reload the page if you login with an attempt to become root and that attempt fails. That ought to be a fairly rare case, and it's exactly the case that is causing all the trouble over in #20017. That's why everything works properly if you hit reload.