Use the shells background feature to put it into background.

Merged Matthias Fechner requested to merge mfechner/gitlab:fix/puma_background into master

What does this MR do?

Fixes the problem that puma has removed the -d feature. Should fix #299570 (closed)

Does this MR meet the acceptance criteria?

Conformity

Availability and Testing

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

  • Label as security and @ mention @gitlab-com/gl-security/appsec
  • The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
  • Security reports checked/validated by a reviewer from the AppSec team