OpenShift installation fails to populate proxy on master node when configured via custom manifest

Issue

When installing OCP the machine-config cluster operator is not successful and complains with following message:

Error:

Message: Node master-0 is reporting: "unexpected on-disk state validating against rendered-master-xx: content mismatch for file \"/etc/mco/proxy.env\"", Node master-1 is reporting: "unexpected on-disk state validating against rendered-master-xx: content mismatch for file \"/etc/mco/proxy.env\"", Node master-2 is reporting: "unexpected on-disk state validating against rendered-master-xx: content mismatch for file \"/etc/mco/proxy.env\""