make pod run as non-root mandatory

[nicolasburtey]

having some Pod running as root can be a security threat, because if someone were to get access to the Pod, then they could install everything they want on it and make further progress to the cluster.

Also, it seems some cloud provider (Openshift from RedHat) denies installation of pods with root access.

Some Pod currently running as root (list not exhaustive):

• db backup
• lnd