Remove sleeps from workers, use schedules

[daronco]

Some workers have sleep calls inside of them, to wait for a while before executing. See https://github.com/mconf/bigbluebutton_rails/blob/master/app/workers/bigbluebutton_meeting_updater.rb#L9

This is bad because it locks the worker until the sleep is done, so the overall time it takes to run the worker is the process time plus the sleep time. Workers that take longer are bad because there is usually a limited amount of workers processing jobs in an application.

There are better ways of doing it using resque. One of the possibilities is to use resque-scheduler to schedule the execution of the worker, so the wait will be done by the scheduler and will not have any influence in the time it takes to run the worker.