DERBY-6053 (Client should use a prepared statement rather than regular statement for Connection.setTransactionIsolation)

Backporting changes from 10.9 into 10.8.

junit and derbyall ran fine on 10.8 with these changes backported.



git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/branches/10.8@1451397 13f79535-47bb-0310-9956-ffa450edef68