intermediate
Fixes for 500 error to not be treated like 404
Fixes for 500 error to not be treated like 404
Fixes for 500 error to not be treated like 404
Merge pull request #51 from pantheon-systems/20130417-asu-delete-parent-when-root

Distinguish between 404 and 500 in update_directory; don't do stat cache deleting for 500.
1. Changed valhalla.py to artificially return 404, then 500, to test checking error code for 404
2. Did error injection on fusedav to simulate 404 and 500 to check code paths