@Override
  public void toStringClassDetails(StringBuilder sb) {
    super.toStringClassDetails(sb);
    if (this.targetServer != null) sb.append(", target=").append(this.targetServer);
  }
Leave here only for checking if we can successfully start the master.
@deprecated Do not use any more.
@see TransitRegionStateProcedure
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/AssignProcedure.java