Update API discovery cache even when incomplete

[JustinKuli]

Previously, if there were any APIs having issues on the cluster, no new API information could be used by the controller. Now, partial results can still be updated. Additionally, API discovery errors during startup will not prevent the controller from functioning at all.

Refs:

• https://issues.redhat.com/browse/ACM-5491

[JustinKuli]

I was considering reporting the controller as unhealthy if the API discovery was having an error, but I realized that restarting the container (which is what kubernetes will do when it's unhealthy) won't be likely to fix anything. It would be easy to add that in though, see https://github.com/JustinKuli/config-policy-controller-1/tree/5491-incomplete-server-apis.

Additionally, @mprahl suggested that we take a more similar approach to the API discovery as in the dependency-watches library: stolostron/kubernetes-dependency-watches#8. I think that is a good longer-term solution, but this controller shares the API information with the templates library, and I would rather have a smaller fix in sooner, rather than a bigger one in multiple places that could be tricky to coordinate.

[openshift-ci]

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