CI: backup specs fail if pipelines collide.

Summary

On 2019-04-24, https://gitlab.com/charts/gitlab/pipelines/58241735 stomped on https://gitlab.com/charts/gitlab/pipelines/58241735 due to a commit triggering the pipeline on the branch before the previous production_specs_gke completed, leaving the database in an restored but not migrated state.

Changes added in 94ad542a resulted in the mysterious output of the wait-for-deps script.

Steps to reproduce

See https://gitlab.com/charts/gitlab/pipelines/58241735

1. Push a commit
2. Wait for production_specs
3. Push another commit

Current behavior

(What you're experiencing happening)

Expected behavior

(What you're expecting to happen)

Versions

• Chart: (tagged version | branch | hash git rev-parse HEAD)
• Platform:
  • Cloud: (GKE | AKS | EKS | ?)
  • Self-hosted: (OpenShift | Minikube | Rancher RKE | ?)
• Kubernetes: (kubectl version)
  • Client:
  • Server:
• Helm: (helm version)
  • Client:
  • Server:

cc @twk3