rcfiles

- Fix usage message.
- Better not_in_toolbox function and usage. The function now checks if
  in a Toolbox container and fails accordingly. All of the usage cases
were like that so now calling the function is a little cleaner.
- Fixup for the last commit. If the Toolbox container was just created,
  it's not running and then `podman exec` fails. Running a simple
`toolbox run true` fixes this.