Velero plugin containers `imagePullPolicy` override

Currently Velero has a set of initContainers that are conditionally deployed/used to add plugins to the Velero deployment (located in this file).

There is no easy way for a customer to override the imagePullPolicy set on these containers. The desired solution would be to use the override for the default Velero imagePullPolicy on all init containers, and default to IfNotPresent when that is not specified.

Example of change to init container (note: hasn't been tested):

  - name: velero-plugin-for-aws
    image: registry1.dso.mil/ironbank/opensource/velero/velero-plugin-for-aws:v1.2.0
    imagePullPolicy: {{ dig "image" "pullPolicy" "IfNotPresent" .Values.addons.velero.values }}

With this in place a customer could specify:

addons:
  velero:
    image:
      pullPolicy: Always

as a values override and it would apply to both the Velero deployment and all initContainers. When not specified this would default to IfNotPresent.

Dev should test deploying with velero and one or more of the plugins to validate that this works as expected. This should only require a BB MR.

AC:

• Values override for pull policy used for all plugin init containers, defaulting to IfNotPresent when that value is not provided