Macaroon update fixes

[btoews]

• d8752b2 - In CI/non-interactive settings, we were trying to open auth.fly.io URLs. When that failed, we printed a message for the user to open the URL and waited for them to do that. Instead, we should fail the 3p discharge attempt. The print-url-and-wait strategy only makes sense in non-local interactive settings (e.g. SSH).
• f90145f - When flyctl has some macaroons and an OAuth token, it checks whether it's missing macaroons for any orgs in order to accommodate for the user being added to new orgs. This behavior makes less sense when flyctl's tokens came from an environment variable instead of from the config file. So, we disable it in that case.