Reservation flag tasks won't run

[orenyk]

Currently, in both config/schedule.rb and lib/tasks/scheduler.rake we're calling the two reservation flag tasks (defined in lib/tasks/flag_reservations.rake) in the global namespace (e.g. rake flag_overdue, etc). Unfortunately, they're defined in the flag_reservations namespace, so if you try to run that Rake task it will tell you Don't know how to build task 'flag_overdue' unless you call rake flag_reservations:flag_overdue. I propose we shorten the namespace for readability (e.g. flag_res) and fix the calls in those files.

[orenyk]

In retrospect, I'm just going to remove the namespace since that's what we do everywhere else.