final void lockedWhenLoading() {
    this.lockedWhenLoading = true;
  }
Will only be called when loading procedures from procedure store, where we need to record
whether the procedure has already held a lock. Later we will call {@link #restoreLock(Object)}
to actually acquire the lock.
hbase-procedure/src/main/java/org/apache/hadoop/hbase/procedure2/Procedure.java