Race observed in TestMultiDimensionalQueueAlgorithmSlowConsumerEffects test.

[pstibrany]

Race observed in TestMultiDimensionalQueueAlgorithmSlowConsumerEffects test.

==================
WARNING: DATA RACE
Write at 0x00c0003ba0b8 by goroutine 2879:
  github.com/grafana/mimir/pkg/scheduler/queue.(*tenantQuerierAssignments).setup()
      /__w/mimir/mimir/pkg/scheduler/queue/tenant_querier_assignment.go:423 +0xc4
  github.com/grafana/mimir/pkg/scheduler/queue.(*MultiQueuingAlgorithmTreeQueue).Dequeue()
      /__w/mimir/mimir/pkg/scheduler/queue/multi_queuing_algorithm_tree_queue.go:85 +0x115
  github.com/grafana/mimir/pkg/scheduler/queue.TestMultiDimensionalQueueAlgorithmSlowConsumerEffects.func1()
      /__w/mimir/mimir/pkg/scheduler/queue/multi_queuing_algorithm_tree_queue_benchmark_test.go:485 +0xc9b
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:1690 +0x226
  testing.(*T).Run.gowrap1()
      /usr/local/go/src/testing/testing.go:1743 +0x44

Previous read at 0x00c0003ba0b8 by goroutine 2880:
  github.com/grafana/mimir/pkg/scheduler/queue.(*queueBroker).dequeueRequestForQuerier()
      /__w/mimir/mimir/pkg/scheduler/queue/tenant_queues.go:152 +0x146
  github.com/grafana/mimir/pkg/scheduler/queue.(*RequestQueue).trySendNextRequestForQuerier()
      /__w/mimir/mimir/pkg/scheduler/queue/queue.go:422 +0x76
  github.com/grafana/mimir/pkg/scheduler/queue.(*RequestQueue).dispatcherLoop()
      /__w/mimir/mimir/pkg/scheduler/queue/queue.go:340 +0x364
  github.com/grafana/mimir/pkg/scheduler/queue.(*RequestQueue).starting.gowrap1()
      /__w/mimir/mimir/pkg/scheduler/queue/queue.go:289 +0x33

Goroutine 2879 (running) created at:
  testing.(*T).Run()
      /usr/local/go/src/testing/testing.go:1743 +0x825
  github.com/grafana/mimir/pkg/scheduler/queue.TestMultiDimensionalQueueAlgorithmSlowConsumerEffects()
      /__w/mimir/mimir/pkg/scheduler/queue/multi_queuing_algorithm_tree_queue_benchmark_test.go:422 +0x1e04
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:1690 +0x226
  testing.(*T).Run.gowrap1()
      /usr/local/go/src/testing/testing.go:1743 +0x44

Goroutine 2880 (running) created at:
  github.com/grafana/mimir/pkg/scheduler/queue.(*RequestQueue).starting()
      /__w/mimir/mimir/pkg/scheduler/queue/queue.go:289 +0x8d
  github.com/grafana/mimir/pkg/scheduler/queue.TestMultiDimensionalQueueAlgorithmSlowConsumerEffects.func1()
      /__w/mimir/mimir/pkg/scheduler/queue/multi_queuing_algorithm_tree_queue_benchmark_test.go:442 +0x486
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:1690 +0x226
  testing.(*T).Run.gowrap1()
      /usr/local/go/src/testing/testing.go:1743 +0x44
==================