int getNumRegionsOnFavoredNodeByPosition(FavoredNodesPlan.Position position) {
    return favoredNodes[position.ordinal()];
  }
Return the number of regions based on the position (primary/secondary/ tertiary) assigned to
their favored nodes
@return the number of regions
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/AssignmentVerificationReport.java