Code review comment for ~ec0/charm-nagios:readonly-account

A package update will not likely replace the existing config, so Juju
will still be authoritative (.orig?).

My point is more of now we have to manage and maintain the config
file. If that changes upstream in the latest nagios package (say with
new config options / features), we'd have to pull it into the
charm. So now the next upgrade-charm could potentially ship out a new
config with options to an environment that has nagios packages that
probably doesn't yet support the new configs (Xenial on Trusty for
example)?

I'm more in favor of just reading in the current config and only
modifying/adding the config otpions we're interested in (in this case,
it's just authorized_for_read_only). If the charm was to be deployed
in a new distro or nagios release where cgi.cfg has introduced newer
config options, then it would still just work (unless ofcourse the
authorized_for_read_only is renamed or removed heh).