Do not mutate original gitlab_address value in e2e tests

What does this MR do and why?

There seems to be an issue where somehow context check can raise an error because gitlab_address got set to empty string which results in uri.host returning nil: https://gitlab.com/gitlab-org/gitlab/-/jobs/6588552717#L902

Investigate the root cause.

Related to: gitlab-org/quality/quality-engineering/team-tasks#2581 (closed)

Fix test mutating global gitlab_address value by removing scheme from it which in turn causes uri.host to not be able to detect host correctly and return nil.

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