house_keeping deletes file before cache is invalidated

[keithrozario]

For /listScans the house_keeping.py function will delete the file, but CloudFront might still cache the old entries -- creating an invalid request for a deleted scan file.

[keithrozario]

Solution options:

• Invalidate CloudFront Cache on upload (1/2 cent per invalidation.... 15 cents per month)
• keep file on folder, but update meta-data. Update listScans to only display files without meta-data (lambda would run longer)
• lambda will always neglect to display the oldest file -- i.e. it'll automatically be removed from viewing before it gets cleaned up