[charts/portal] Rabbit upgrade

[melil02]

Description of the change

Added explicit declaration of vhost / for new verion of rabbitmq

Benefits

Fixing fresh install of rabbit on helm

Drawbacks

None

Applicable issues

• fixes #

Additional information

Checklist

• [] 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

[jmmAVGO]

Please ignore my previous comment; when I used the correct branch, this seemed to work