`juju wait-for model` freezes on live model

[Jordan Barrett]

I have some models for which `juju wait-for model` returns the expected answer immediately:
```
$ juju wait-for model m
Model "m" is running
properties:
  life: alive
  status: available
```
and others for which it just freezes until it times out.

Both models are in a live and stable state, and I can't see any difference between them. So I'm afraid I have no idea what's causing this.

```
$ juju version --all
version: 3.0.3-ubuntu-amd64
git-commit: ae342ed49fbaa5a3d3fa9193612e1df414aa8785
```

[Joseph Phillips (manadart)]

wait-for uses a multi-watcher via the API (so a websocket). It is supposed to reconnect if it drops, but maybe there's an issue with that logic.

That or we're not getting all deltas, which is a little more concerning.

[Samuel Allan (samuelallan)]

https://bugs.launchpad.net/juju/+bug/2019515 is possibly related, but also probably not going by the description of "some models for which ...".