When using a nested declarative Kubernetes agent, it implicitly uses the current PodTemplateContext as parent template.

https://github.com/jenkinsci/kubernetes-plugin/blob/46cdc75063dc5617445972a08eaead460457af28/src/main/java/org/csanchez/jenkins/plugins/kubernetes/pipeline/PodTemplateStepExecution.java#L85

There are 2 situations when this can lead to unexpected behaviors : 

• declaring explicit inheritFrom will not work without displaying any clear warning
• When scheduling a pod template on a specific machine, where a limited set of images are allowed to run, it can fail running the slave.

To avoid such situation, what do you think about those 2 solutions : 

• inheritFrom has priority over template context.
  • When it is empty, no parent context will be used
  • When null, the current template context will be used (current behavior)
  • when non null and not empty, use it as the parent template
• Add a new option to avoid implicit template inheritance