Fix sqlite driver memory eating due to close failure

Fix sqlite driver memory eating due to close failure

If an ongoing query is not finalized before close function is
called, sqlite driver still tries to close the connection to
sqlite. In this case, sqlite reports an error to sqlite driver
which is not reported to the client. The failure in close causes
connection to sqlite unclosed and memory is not freed. This
fix tries to finalize all queries before close function is called.
The close function should succeed.

Task-number: QTBUG-16967
Reviewed-by: Charles Yin