Add parameter for NameNode to process getBloks request

HDFS-13183  add a nice feature that Standby NameNode can process getBlocks request to reduce Active load.  Namenode must set  `dfs.ha.allow.stale.reads = true` to enable this feature. However, if we  set `dfs.ha.allow.stale.reads = true`, Standby Namenode will be able to  process all read requests, which may lead to yarn jobs fail  because  Standby Namenode is stale . 

Maybe we should add a config `dfs.namenode.get-blocks.check.operation=false` for namenode to disable check operation  when namenode process getBlocks request.