Serve products from opus server

[rfrenchseti]

• Fixes #1091
• Were any Django, import pipeline, table_schema, or dictionary files modified? Y
  • If YES:
  • Database used: opus3_test_200729
  • All Django tests pass: Y
  • FLAKE8 run on modified code: Y
• Were any JavaScript or CSS files modified? N
  • If YES:
  • JSHINT run on all affected files: NA
  • Tested on Chrome, Firefox, Safari, Edge, and iOS: NA (Remember to test all browser sizes)
  • Tested for race conditions (with delayed API calls if applicable): NA

Description of changes:

Serve all product files from opus.pds-rings.seti.org instead of pds-rings.seti.org

Known problems: