Invalid errors are reported in a CA-less IPA installation

[rcritten]

Some invalid errors are reported by ipa-healthcheck in a CA-less installation.

This one by healthcheck itself:

  {
    "source": "ipahealthcheck.ipa.roles",
    "check": "IPACRLManagerCheck",
    "result": "CRITICAL",
    "uuid": "17c830ea-7384-4d60-ba52-86bb4991c412",
    "when": "20210511153916Z",
    "duration": "0.000073",
    "kw": {
      "exception": "Unable to read /var/lib/pki/pki-tomcat/conf/ca/CS.cfg"
    }
  },

And a bunch of these by the pki plugin. We may need to filter out this plugin if the CA is not configured.

  {
    "source": "pki.server.healthcheck.certs.expiration",
    "check": "CASystemCertExpiryCheck",
    "result": "CRITICAL",
    "uuid": "8135159e-c551-44ba-89da-5cff80e54c16",
    "when": "20210511153916Z",
    "duration": "0.000104",
    "kw": {
      "msg": "Invalid PKI instance: pki-tomcat"
    }
  },

[rcritten]

I implemented ca_configured right originally, then ended up breaking it again.

Other things can consume the core ipahealthcheck engine so I need to be careful not to impose too many IPA-isms into it.

One of those consumers is dogtag which has its own pki-healthcheck.

So this means we need to be able to run in these conditions:

1. IPA is configured with a CA: the pki checks are run
2. IPA is configured without a CA: the pki checks are not run
3. IPA is not configured: the pki checks are run

Which basically equates to three states: True, False, None

This was done originally with the ca_configured variable set to None. Using some inside knowledge the registries are loaded which will set ca_configured to True or False in the IPA registry. Using that we can determine if the pki checks should be available. Unfortunately I changed the initialization to False so it always assumes that IPA is installed. ca_configured will be False for the case of IPA not installed instead of None so we can't handle that last state.

So I just need to flip it back to None and add a bunch of comments since this is not at all obvious.