[charts/portal] Parametrize imagePullPolcy for all three portal jobs: db-upgrade-portal, db-upgrade-rbac and cert-upgrade

[cuisimon]

Description of the change

Parametrize imagePullPolcy for all three portal jobs: db-upgrade-portal, db-upgrade-rbac and cert-upgrade.

Benefits

To fix the issue that db-upgrade-portal image not being updated even there is newer image.

Drawbacks

Applicable issues

• fixes #

Additional information

Checklist

• [X] Chart version bumped in Chart.yaml according to semver.
• [X] Variables are documented in the README.md
• [X] Title of the PR starts with chart name (e.g. [charts/gateway])
• [X] If the chart contains a values-production.yaml apart from values.yaml, ensure that you implement the changes in both files