text: Title: imagePullPolicy when defined without a value defaults to Always not to IfNotPresent 
  Body: <!-- Please only use this template for submitting enhancement requests -->
  
  **What would you like to be added**:
  
  The documentation suggests that "The default pull policy is IfNotPresent"
  This is not the case when imagePullPolicy is defined under the spec section in a Pod definition without a specific value. 
  
  Example:
  ```
  apiVersion: v1
  kind: Pod
  metadata:
    labels:
      run: nginx-test
    name: nginx-test
  spec:
    containers:
    - image: nginx
      name: nginx-test
    imagePullPolicy:
  
  ```
  This will result in a Pod having imagePullPolicy as Always.
  
  **Why is this needed**:
  
  This is needed for clarification of the default behaviour.
  It is necessary for the appropriate handling of helm charts, in cases that the imagePullPolicy is empty.
  