fix(chart): correct default values for init containers and additional volumes

[jnels124]

Pull Request template

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Why is this PR required? What issue does it fix?:
Fixes a small config error in default values.yaml

What this PR does?:
initializes to an object instead of array
Does this PR require any upgrade changes?:
no
If the changes in this PR are manually verified, list down the scenarios covered::
Applied chart and verified warnings were gone and values functioned as intended
Any additional information for your reviewer? :
Mention if this PR is part of any design or a continuation of previous PRs

Checklist:

• Fixes Default value in values.yaml triggers warning message on install #474
• PR Title follows the convention of <type>(<scope>): <subject>
• Has the change log section been updated?
• Commit has unit tests
• Commit has integration tests
• (Optional) Are upgrade changes included in this PR? If not, mention the issue/PR to track:
• (Optional) If documentation changes are required, which issue on https://github.com/openebs/openebs-docs is used to track them:

[niladrih]

@jnels124 arrays seem appropriate with initContainers and volumes. Why is this change required?

[jnels124]

@niladrih because the expected structure of the config is as such:

zfsNode:
   additionalVolumes:
     node:
       hostPath:
         path: /
     scripts:
       configMap:
         name: "{{ .Release.Name }}-zfs-init"
         defaultMode: 0744

The key for the additionalVolumes dict is used in the template and the template requires this structure