iso/pxe customize --ignition-ca doesn't set CA for coreos.inst.ignition_url

[bgilbert]

The Ignition config specified by --ignition-url or coreos.inst.ignition_url is fetched by coreos-installer and not by Ignition, so iso/pxe customize --ignition-ca doesn't affect it. At least one user has been confused by this. PXE users might not want to use --dest-ignition because then they'd have to create one custom image per Ignition config, rather than one per network environment.

Consider extending --ignition-ca to inject CA certificates in a way that will affect coreos-installer install in the live system (making the option name slightly misleading). Another possibility is to add a new option that produces a similar result.

OpenShift docs bug.