void addReplicaToPartition(AmbryPartition partition, AmbryReplica replica) {
      if (!partitionToReplicas.containsKey(partition)) {
        partitionToReplicas.put(partition, new ArrayList<>());
      }
      partitionToReplicas.get(partition).add(replica);
    }
Associate the replica with the given partition.
@param partition the {@link AmbryPartition}.
@param replica the {@link AmbryReplica}.
ambry-clustermap/src/test/java/com/github/ambry/clustermap/DynamicClusterManagerComponentsTest.java