Fixes warning 'method redefined' in scaffold generators tests

- f1805a697831 Redefined 'test_scaffold_generator_no_assets' twice.
- Only the last instance of these three definitions of the same method
  was getting called when the tests were actually running.
- This commit changes names of this method so that all three
  definitions will be called
- scaffold.css is not generated by --assets=false switch.
- Test was expecting the presence of the file with --assets=false
- This issue was not discovered in f1805a697831b because it was
  redefining the same method twice