Test db cleanup

Test db cleanup
* Fix Oracle stuff per CR on r88755
* Don't expect tests to clean up after themselves, do it in MediaWikiTestCase::run() (skipping user and interwiki, also per CR)
** Also don't do it from the destructor, phpunit calls this more often than you'd think
* Need to find: way to detect "is this the last test?" so we can drop our tables on completion