Remove the frequency restriction on scheduler runs

Celery seems to have problems where it won't run tasks of different
types if there is still a backlog of tasks of one type, even if that
task type has restrictions on frequency.  This can become a problem
whenever there is a backlog assign_tasks tasks for whatever reason.
Commit db transactions before running scheduler

This seems to help with some weird race conditions.
Merge pull request #203 from guidow/fixes_for_celery_tasks

Fixes for celery tasks