Fix some list comprehensions that I thought were generator comprehensions.

Fix some list comprehensions that I thought were generator comprehensions.

Apparently [x for x in whatever] yields a list, not an iterator, which means
two things:
  - it might use more memory than I thought
  - you definitely don't need to write list([...]) since it's already a
    list.

Clean up a few of these.  You learn something new every day.