Make PROD_MODE check for a non-false value
Make PROD_MODE check for a non-false value

This also defaults PROD_MODE to "false", which shouldn't affect how
people are currently using the environment variable.

It would ideally check for `!= "true"` but I'm not sure how others are
currently use the environment variable.

hackupc/backend,hackupc/backend,hackupc/backend,hackupc/backend