@Override
  public void addFront(final Procedure procedure, boolean notify) {
    push(procedure, true, notify);
  }
Add the procedure to the queue. NOTE: this method is called with the sched lock held.
@param procedure the Procedure to add
@param addFront  true if the item should be added to the front of the queue
hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/AbstractProcedureScheduler.java