[BUG][Opensearch] init container missing pull policy

[anna-intellegens]

Describe the bug
Persistence init container doesn't have a pull policy defined, meaning it defaults to Always, causing it to error on offline deployments

To Reproduce
Steps to reproduce the behavior:

1. Import all required images to a local machine running kubernetes without external network connection
2. Deploy helm chart with persistence enabled and image.pullPolicy = "Never" set in values.yaml
3. Opensearch fails to start with ErrImagePull and ImagePullBackOff due to persistence init container

Expected behavior
Persistence init container should respect pull policy specified in image.pullPolicy similar to other init containers (such as sysctlInit)

Chart Name
Opensearch v1.x charts

Screenshots
If applicable, add screenshots to help explain your problem.

Host/Environment (please complete the following information):

• Helm Version: Tested on both v3.9.1+unreleased (microk8s bundled) and v3.16.2
• Kubernetes Version: Tested on both Microk8s 1.31, and 1.29.7 via Minikube

[prudhvigodithi]

[Triage]
Thanks @anna-intellegens for opening a PR, we can get the PR reviewed and merged.
@peterzhuamazon