Review App credentials does not reliably work

Capturing the challenges from https://gitlab.slack.com/archives/C0AR2KW4B/p1541455696323000

The workaround here is to re-deploy the review app to make sure we get the recent credentials.

This is also affecting our ability to test Rails 5 https://gitlab.com/gitlab-org/gitlab-ce/issues/51719#note_114706693

We are also seeing instability when redeploying the app. See https://gitlab.com/gitlab-org/gitlab-ee/-/jobs/112364180