Issue reported by @jarodreyes.
The user was not informed that `fleetctl login` was using the PASSWORD
environment variable:
`main`:
```sh
export PASSWORD=wrong
fleetctl login
Log in using the standard Fleet credentials.
Email: a@b.c
Error: Login failed: login received status 401 Authentication failed: Authentication failed
```
And with the changes on this PR:
```
export PASSWORD=wrong
fleetctl login
Log in using the standard Fleet credentials.
Email: a@b.c
Using value of environment variable $PASSWORD as password.
Error: Login failed: login received status 401 Authentication failed: Authentication failed
```