docker-compose-prod with tmp shared

[kennethrioja]

Summary of changes

• Adding /tmp as a shared volume with app and sidekiq

Motivation and context

• While running source test on prod, the running test finishes with a "There was a problem rendering the results.", the results file (test_results_#{id}.yml) was in tmp on the sidekiq instance, but not in the tess instance. @fbacall confirmed /tmp should be on a shared volume. Then while doing the test on a local docker I can see that the test_results.yml is found in both /tmp but this is explained by the shared ./code volume between app and sidekiq (see docker-compose.yml). However in docker-compose-prod.yml it is /code/public/system which is shared between app and sidekiq and not /tmp. Fixing it now.

Checklist

• I have read and followed the CONTRIBUTING guide.
• I confirm that I have the authority necessary to make this contribution on behalf of its copyright owner and agree
  to license it to the TeSS codebase under the
  BSD license.

[fbacall]

Also needs tmp: adding to the list of volumes at the bottom of the file