WIP: Force shell scripts to run as bash for consistent output formatting

What does this MR do?

This MR forces the shell scripts in this project to run in bash. @iamricecake and I have both had issues with newlines characters being recorded as actual newlines or \n in test 3, and forcing to bash makes this work, at least on OSX.

However, forcing to bash seems to make the jobs fail on CI. Further investigation is needed.

What are the relevant issue numbers?

No open issues AFAIK.

Does this MR meet the acceptance criteria?

100% not.

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
  • Auto-DevOps template (also in CE)
  • Job definition example
  • CI Templates (to be removed)
  • Vendored CI Templates (also in CE)
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer