OpenShift 4 Agent-Based Installer fails in disconnected environments

Issue

• The installation fails when using the Agent-Based Installer in a disconnected environment.

• The command openshift-install agent wait-for install-complete returns the following error:

  INFO Unable to retrieve cluster metadata from Agent Rest API: no clusterID known for the cluster
  

• The journal logs show error messages like the following ones:

  level=warning msg="command 'oc adm release info -o template --template '{{.metadata.version}}' --insecure=true --icsp-file=/tmp/icsp-file000000000 mirror.example.com:8443/openshift/release-images@sha256:xxxxxx --registry-config=/tmp/registry-config000000000' exited with non-zero exit code 1: \nFlag --icsp-file has been deprecated, support for it will be removed in a future release. Use --idms-file instead.\nerror: image \"mirror.example.com:8443/openshift/release-images@sha256:xxxxxx\" not found: manifest unknown: manifest unknown\n"
  level=error msg="failed to get image openshift version from mirror release image mirror.example.com:8443/openshift/release-images@sha256:xxxxxx" error="command 'oc adm release info -o template --template '{{.metadata.version}}' --insecure=true --icsp-file=/tmp/icsp-file000000000 mirror.example.com:8443/openshift/release-images@sha256:xxxxxx --registry-config=/tmp/registry-config000000000' exited with non-zero exit code 1: \nFlag --icsp-file has been deprecated, support for it will be removed in a future release. Use --idms-file instead.\nerror: image \"mirror.example.com:8443/openshift/release-images@sha256:xxxxxx\" not found: manifest unknown: manifest unknown\n"
  level=fatal msg="Failed to register cluster with assisted-service: command 'oc adm release info -o template --template '{{.metadata.version}}' --insecure=true --icsp-file=/tmp/icsp-file000000000 mirror.example.com:8443/openshift/release-images@sha256:xxxxxx --registry-config=/tmp/registry-config000000000' exited with non-zero exit code 1: \nFlag --icsp-file has been deprecated, support for it will be removed in a future release. Use --idms-file instead.\nerror: image \"mirror.example.com:8443/openshift/release-images@sha256:xxxxxx\" not found: manifest unknown: manifest unknown\n"
  

  level=error msg="failed to get openshift version from mirror release image mirror.example.com:8443/ocp/openshift-release-dev/ocp-release@sha256:xxxxxx" error="command 'oc adm release info -o template --template '{{.metadata.version}}' --insecure=false --idms-file=/tmp/idms-file000000000 quay.io/openshift-release-dev/ocp-release@sha256:xxxxxx --registry-config=/tmp/registry-config000000000' exited with non-zero exit code 1: \nerror: unable to read image quay.io/openshift-release-dev/ocp-release@sha256:xxxxxx: Get \"https://quay.io/v2/\": tls: failed to verify certificate: x509: certificate signed by unknown authority\n"
  level=warning msg="command 'oc adm release info -o template --template '{{.metadata.version}}' --insecure=false --idms-file=/tmp/idms-file000000000 quay.io/openshift-release-dev/ocp-release@sha256:xxxxxx --registry-config=/tmp/registry-config000000000' exited with non-zero exit code 1: \nerror: unable to read image quay.io/openshift-release-dev/ocp-release@sha256:xxxxxx: Get \"https://quay.io/v2/\": tls: failed to verify certificate: x509: certificate signed by unknown authority\n"
  level=fatal msg="Failed to register cluster with assisted-service: command 'oc adm release info -o template --template '{{.metadata.version}}' --insecure=false --idms-file=/tmp/idms-file000000000 quay.io/openshift-release-dev/ocp-release@sha256:xxxxxx --registry-config=/tmp/registry-config000000000' exited with non-zero exit code 1: \nerror: unable to read image quay.io/openshift-release-dev/ocp-release@sha256:xxxxxx: Get \"https://quay.io/v2/\": tls: failed to verify certificate: x509: certificate signed by unknown authority\n"