Do not add /cache volume if already provided by the user

This is a general Merge Request template. Consider to choose a template from the list above if it will match your case more.

What does this MR do?

Only adds the default /cache volume if it is not specified using the docker-volumes option, see #2538 (closed)

Why was this MR needed?

See #2538 (closed)

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Branch has no merge conflicts with master (if you do - rebase it please)

What are the relevant issue numbers?

Closes #2538 (closed)