message: upstream: fix PriorityStateManager indexing
  The PriorityStateManager is indexing off the end of an array when the priority is large enough:
  Risk Level: Low
  Testing: Verified that the out-of-bounds indexing is actually happening by testing with an additional assert.
  Docs Changes: N/A
  Release Notes: N/A
diff: @@ -695,7 +695,8 @@ void PriorityStateManager::updateClusterPrioritySet(
  HostVectorSharedPtr hosts(std::move(current_hosts));
  LocalityWeightsMap empty_locality_map;
  LocalityWeightsMap& locality_weights_map =
  - priority_state_.empty() ? empty_locality_map : priority_state_[priority].second;
  + priority_state_.size() > priority ? priority_state_[priority].second : empty_locality_map;
  + ASSERT(priority_state_.size() > priority || locality_weights_map.empty());
  LocalityWeightsSharedPtr locality_weights;
  std::vector<HostVector> per_locality;
  