[hbase-connectors] Duplicate result when searching HBase by Spark

I've used hbase-connector for querying HBase table by Spark, and the following issue is what I've encountered recently:

When I run SQL:

select * from hbase_tabe where rowkey in ('r1', 'r2') or rowkey='r1'

I've got duplicate row "r1" in results.
In HBaseTableScanRdd, buildGets method forms two duplicate GET request for rowkey "r1". I think we might need a Set to make sure duplicate rowkey won't be request.