Quick tunnel is an annoying default for bad commands

If an invalid command is run, the default is now to start a quick tunnel, instead of printing help or anything. I think this is confusing and annoying.

For example, sometimes I type `cloudflared auth` instead of `cloudflared login`, or `cloudflared tunnel status` instead of `cloudflared tunnel list`, and am greeted with:

```
$ cloudflared auth
2021-09-07T15:09:03Z INF Thank you for trying Cloudflare Tunnel. Doing so, witho
ut a Cloudflare account, is a quick way to experiment and try it out. However, b
e aware that these account-less Tunnels have no uptime guarantee. If you intend
to use Tunnels in production you should use a pre-created named tunnel by follow
ing: https://developers.cloudflare.com/cloudflare-one/connections/connect-apps
2021-09-07T15:09:03Z INF Requesting new quick Tunnel on trycloudflare.com...
^C
$ cloudflared login
A browser window should have opened at the following URL:
```

Even `cloudflared asdf` starts a quick tunnel. I don't think this should be the default behavior when the user is trying to do something specific, and uses an unrecognized command - they're almost certainly not likely trying to start a quick tunnel.

I wonder how many quick tunnels have been started by mistake, as opposed to intentionally to try out tunnels. I'd expect this to have a large effect on Cloudflare's measured metrics for quick tunnel usage.