LoadBalancerTest: Clean up transaction handling for sqlite

LoadBalancerTest: Clean up transaction handling for sqlite

We need to make sure a DBO_TRX transaction was started before doing the
CREATE TABLE, because CREATE TABLE itself won't start one and sqlite
breaks if schema changes are done on one handle while another is open.

Also, incidentally, have the handles in these LoadBalancerTests log to
the standard channel. And clean up the auto-rollback of DBO_TRX
transactions to use ->rollback() instead of ->doRollback() plus
incorrect manual setting of trxStatus.

Bug: T191863
Change-Id: Ib422ef89e7eba21281e6ea98def9f98ae762b9fe