proxy-init container doesn't set runAsNonRoot: false

[dhduvall]

Describe the bug
When a pod has a securityContext, all its containers inherit that and have the option of overriding each setting in that map. If this podSecurityContext includes runAsNonRoot: true, then the proxy-initcontainer fails to run, because it requires running as root. The webhook does set runAsUser: 0, so I assume this is an oversight rather than a deliberate choice.

Steps To Reproduce
Create a pod configured to use workload identity and the annotation azure.workload.identity/inject-proxy-sidecar: "true", and include a spec.securityContext that includes runAsNonRoot: true. I ran into this installing the Hashicorp Vault Helm chart. Vault doesn't support MSAL yet, so it requires the proxy to use WI.

Expected behavior
The proxy-init initContainer starts and executes correctly.

Logs
Scrolled off-screen, I'm afraid; the events in the output of kubectl describe pod are where the complaint can easily be found.

Environment

• Kubernetes version (use kubectl version): server=1.23.12
• Cloud provider or hardware configuration: Azure AKS

Additional context
I have a fix which works for me. I'll submit it as a PR.