## What changes were proposed in this pull request?
Likewise [DataSet.scala](https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala#L156) KeyValueGroupedDataset should mark the queryExecution as transient.
As mentioned in the Jira ticket, without transient we saw serialization issues like
```
Caused by: java.io.NotSerializableException: org.apache.spark.sql.execution.QueryExecution
Serialization stack:
- object not serializable (class: org.apache.spark.sql.execution.QueryExecution, value: ==
```
## How was this patch tested?
Run the query which is specified in the Jira ticket before and after:
```
val a = spark.createDataFrame(sc.parallelize(Seq((1,2),(3,4)))).as[(Int,Int)]
val grouped = a.groupByKey(
{x:(Int,Int)=>x._1}
)
val mappedGroups = grouped.mapGroups((k,x)=>
{(k,1)}
)
val yyy = sc.broadcast(1)
val last = mappedGroups.rdd.map(xx=>
{ val simpley = yyy.value 1 }
)
```
Author: Ergin Seyfe <eseyfe@fb.com>
Closes#15706 from seyfe/keyvaluegrouped_serialization.
8a538c97b5