Bug #11766851 QUERYING I_S.PARTITIONS CHANGES THE CARDINALITY OF THE

              PARTITIONS.

ANALYSIS
--------
Whenever we query I_S.partitions,
ha_partition::get_dynamic_partition_info()
is called which resets the cardinality 
according to the number of rows in last
partition.

Fix
---
When we call get_dynamic_partition_info() 
avoid passing the flag HA_STATUS_CONST
to info() since HA_STATUS_CONST should 
ideally not be called for per partition.

[Approved by mattiasj rb#2830 ]

sql/ha_partition.cc

@@ -5887,7 +5887,7 @@ void ha_partition::get_dynamic_partition_info(PARTITION_STATS *stat_info,
                                               uint part_id)
 {
   handler *file= m_file[part_id];
-  file->info(HA_STATUS_CONST | HA_STATUS_TIME | HA_STATUS_VARIABLE |
+  file->info(HA_STATUS_TIME | HA_STATUS_VARIABLE |
              HA_STATUS_VARIABLE_EXTRA | HA_STATUS_NO_LOCK);
 
   stat_info->records=              file->stats.records;