Podpresets don't work for statefulsets

[anhi]

The webhook works fine when using deployments, but when I switch from deployment to a statefulset (keeping everything else identical), it stops working. Debugging the code, it seems that listing the podpresets does not work for pods created from a statefulset when using the pod namespace as an option.

[dpoetzsch]

This seems to work now with the current master (4bf4993).