Extract fixture functions to make things more legible.
More descriptive name for the test.
Extract addExecutors, rename availableSlotsByServer -> slots.
Similarly test bolts and statespouts.
Prove we don't schedule storm system components.
More tests for Schedule.

Looks like we broke ExecutorPreference yesterday, standby while that gets cleaned up.
Compare total task and region counts when checking equality.
Prove we can locally schedule two executors at a time.
Only schedule locally where possible.

Also strenghen the negative tests by using any(WorkerSlot.class).