Pat ran into a weird error when trying to do some development agains
the testing cloud:
```
$ pulumi logout
$ pulumi login --cloud-url [test-cloud-url]
Logged into [test-cloud-url]
$ pulumi stack ls
Enter your Pulumi access token from https://pulumi.com/account:
```
In his case, we did not have `current` set in our credentials.json
file (likely due to him calling `pulumi logout` at some point) but we
did have stored credentials for that cloud. When he logged in the CLI
noticed we could reuse the stored credentials but did not update the
the current setting to set the current cloud.
While investigating, I also noticed that `logout` did not always do
the right thing when you were logged into a different backend than
pulumi.com
94d11884f8