Red Hat OpenShift 4 IPI installation on OpenStack fails with error "ignition ... GET error ... x509: certificate signed by unknown authority"

Issue

• OpenStack endpoints use a custom PKI or self signed certificate

• Ignition reports (OpenShift 4.2)

  [80558.038518] ignition[666]: GET error: Get https://openstack-controller.example.intern:13808/v1/AUTH_xxxxxxxxxxxxxxxxxxxxxx/xxxx-xxxx/bootstrap.ign?temp_url_sig=xxxxxxxxxxxxxxxxxxxxxxxxxxx&temp_url_expires=xxxxxxxxxxxx: x509: certificate signed by unknown authority
  

• Ignition reports (OpenShift 4.3)

  [   31.816448] ignition[1112]: GET error: Get https://openstack-controller.example.intern:13808/v1/AUTH_xxxxxxxxxxxxxxxxxxxxxx/xxxx-xxxx/abcabc152514abcbabc: x509: certificate signed by unknown authority