NAS-2309, NAS-2308 Converted HarvestSchedulerMonitorServerTester to pure unit test

This include:
 * Converting all external singleton access in HarvestSchedulerMonitorServer to injected dependencies.
 * Converting massive fixture setup in test to mocking of all external components
 * Enabling test class
 * Moving test to core module and renaming to standard *Test postfix
 * Moved THE_SCHED channels definition from Channels to HarvestChannels
 * Rewriting all test methods to focused unit testes based on the current HarvestSchedulerMonitorServer functionality.