Fix executing queries in a different db than default

The problem popped when CubeMetastoreClient caching is changed to create one client per conf, instead of one static client, as part of cube code movement.

Changes include : 
* Fix the way underlying storage tables are calculated in ColumnarSQLReWriter
* Fix the way tables queried and table weights calculated in HiveQueryPlan
* Fix test failures in hive and make hive driver tests run in suite as there is problem running them in parallel wrt session state.
* Fix test failures in jdbc driver
* Fix dropping db in TestQueryRewrite