boolean synchronousBalanceSwitch(final boolean b) throws IOException {
    return switchBalancer(b, BalanceSwitchMode.SYNC);
  }
Assigns balancer switch according to BalanceSwitchMode
@param b    new balancer switch
@param mode BalanceSwitchMode
@return old balancer switch
hbase-server/src/main/java/org/apache/hadoop/hbase/master/MasterRpcServices.java