Code review comment for ~lamoura/update-notifier:show-only-esm-infra-alerts-on-esm-machine

integration Test runs:
#### xenial should prefer infra messages
 # esm-infra and esm-apps disabled
UA Infra: Extended Security Maintenance (ESM) is not enabled.

25 updates can be applied immediately.
1 of these updates is a standard security update.
To see these additional updates run: apt list --upgradable

Enable UA Infra: ESM to receive additional future security updates.
See https://ubuntu.com/esm or run: sudo ua status

# esm-infra enabled
UA Infra: Extended Security Maintenance (ESM) is enabled.

25 updates can be applied immediately.
1 of these updates is a standard security update.
To see these additional updates run: apt list --upgradable

# esm-infra and esm-apps enabled
UA Infra: Extended Security Maintenance (ESM) is enabled.

25 updates can be applied immediately.
1 of these updates is a UA Apps: ESM security update.
1 of these updates is a standard security update.
To see these additional updates run: apt list --upgradable

# esm-apps enabled
UA Infra: Extended Security Maintenance (ESM) is not enabled.

24 updates can be applied immediately.
1 of these updates is a UA Apps: ESM security update.
1 of these updates is a standard security update.
To see these additional updates run: apt list --upgradable

Enable UA Infra: ESM to receive additional future security updates.
See https://ubuntu.com/esm or run: sudo ua status

# Bionic, I'm surprised we don't also have a message about "UA Apps: Extended Security Maintenance (ESM) is enabled." on LTS releases that are not in active ESM (bionic++). I was under the impression that we needed it there when ESM-Apps gets released. This can be handled later, but something we should check on for next Bionic SRU