Expand multiple-redis test

What does this MR do?

This MR was originally created to troubleshoot the gitlab-com/gl-infra/production#5962 (comment 744193012).

It expands our Chart tests.

Related issues

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• [-] Documentation created/updated
• Tests added
• [-] Integration tests added to GitLab QA
• [-] Equivalent MR/issue for omnibus-gitlab opened