Basic Authentication error message is not clear

If snapteld started in the basic auth mode, the API unauthorized error message is not clear.

when no password specified:
```sh
▶ ./build/darwin/x86_64/snaptel task list
Error getting tasks:
Invalid credentials
```

when a wrong password specified:
```
▶ ./build/darwin/x86_64/snaptel -p task list
Password:
Error getting tasks:
Invalid credentials

```