Silenice trx warnings from LoadBalancer.

Silenice trx warnings from LoadBalancer.

This is a follow-up to Idbe4a903.

LoadBalancer::commitMasterChanges used to cause a warning if an implicite
transaction was in progress. This is now supressed.

Note that warnign when an automatic transaction is committed explicitely,
it does make sense to issue a warning. But that should not be done for summary
commits when closing a connection, etc.

Change-Id: Id68c3607f6b9d930c00422baa6658b0651f2e42e