drill

0a2518d7 - DRILL-4363: Row count based pruning for parquet table used in Limit n query.

DRILL-4363: Row count based pruning for parquet table used in Limit n query. Modify two existint unit testcase: 1) TestPartitionFilter.testMainQueryFalseCondition(): rowCount pruning applied after false condition is transformed into LIMIT 0 2) TestLimitWithExchanges.testPushLimitPastUnionExchange(): modify the testcase to use Json source, so that it does not mix with PushLimitIntoScanRule.