When adding a name to the list for a `letsEncrypt` property, certbot fails thusly:

    Saving debug log to /var/log/letsencrypt/letsencrypt.log
    Plugins selected: Authenticator webroot, Installer None
    Missing command line flag or config entry for this setting:
    You have an existing certificate that contains a portion of the domains you requested (ref: /etc/letsencrypt/renewal/…)

    It contains these names: …

    You requested these names for the new certificate: …

    Do you want to expand and replace this existing certificate with the new certificate?

    (You can set this with the --expand flag)

I think maybe Propellor should always pass --expand? I haven't tested if that works correctly when not changing the names.
