Refactored the method refresh_all_ems_timer in ext_management_system.rb to work against the current class. So now when it is called against the ExtManagementSystem class it will refresh all the providers in the zone and when it is called against the EmsMicrosoft class it will only process those sub-classed instances.

The refresh_all_ems_timer method handles selecting the providers in the current zone and that method ultimately calls EmsRefresh.queue_refresh which queues the work with the proper zone and role.