public boolean isLockedWhenLoading() {
    return lockedWhenLoading;
  }
Can only be called when restarting, before the procedure actually being executed, as after we
actually call the {@link #doAcquireLock(Object, ProcedureStore)} method, we will reset
{@link #lockedWhenLoading} to false.
<p/>
Now it is only used in the ProcedureScheduler to determine whether we should put a Procedure in
front of a queue.
hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/Procedure.java