public long getTimestampOfLastAppliedOp() {
    return this.lastTimestampForAge;
  }
Get the TimestampOfLastAppliedOp. If no replication Op applied yet, the value is the timestamp
at which hbase instance starts
@return timeStampsOfLastAppliedOp;
hbase-server/src/main/java/org/apache/hadoop/hbase/replication/regionserver/MetricsSink.java