[charts/portal]:Fixing functional issues that are observed related to enrolling proxy in portal

[ksaladi]

Description of the change

Enrolling proxy in Portal 5.1.2 stable branch was failing due to missing env variables.

Benefits

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

[SatishKoney-BRCM]

update readme too