fix to file.py, returning a list comprehension.

Mimicking items.py and returning a list comprehension of the list, instead
of the list itself. This solves an issue with the apt module:

Before (apt fails):
    <127.0.0.1> REMOTE_MODULE apt package=aptitude
    zip

After (now apt runs fine):
    <127.0.0.1> REMOTE_MODULE apt package=aptitude,zip