Add support for User Namespaces in pods
https://docs.openshift.com/container-platform/4.17/nodes/pods/nodes-pods-user-namespaces.html#nodes-pods-user-namespaces-configuring_nodes-pods-user-namespaces

> Linux user namespaces allow administrators to isolate the container user and group identifiers (UIDs and GIDs) so that a container can have a different set of permissions in the user namespace than on the host system where it is running. This allows containers to run processes with full privileges inside the user namespace, but the processes can be unprivileged for operations on the host machine.

We want to confirm this for 4.18/4.19.