Tests pass for paths chown exceptions

Hi,
The following changes allow all unit tests to pass:
* Default function arguments in the function definitions were interfering with the unit tests' ability to override values from the constants module.
* chown and fchown throw OverflowError exceptions instead of system errors for uid and gids that are negative. These were unexpected by the unit tests and exception handlers designed for OSErrors.
* uninstall() first tries a down() before anything else, which can throw an FSQConfigError. I made changes to allow and expect this in the unit tests.

Total Tests Run: 186149
Total Failures: 0, Total Errors: 0

Merry Christmas.

-tim