CORE-2130 workaround fetchSize exception for oracle jdbc driver

Fix for CORE-2130. Setting fetchSize to zero instead of Integer.MIN_VALUE might as well fix the issue. But I guess somebody had a reason to use negative values instead of 0 and I can't test with any other jdbc driver.

Note that lots of tests fail on my box, but that's with and without my fix. So I couldn't run the whole testsuite.