[DEBUG] Test case for debugging the last index ID bug from Doctrine/MySQL


See https://github.com/owncloud/core/issues/8946#issuecomment-45751508

This commit adds a test case that proves that the last index ID is always returning `0` after an insert whenever `OC_DB::createDbFromStructure()` is called.

You can run the test locally using this command:
`./autotest.sh mysql ../apps/files_encryption/tests/migration.php`

Then you can make it work by commenting out `$this->conn->close()` in the constructor of the `lib/private/db/mdb2schemamanager.php` class.
I think that class probably closes the connection to force transaction closing and make sure we get a clean connection. This has the side effect of breaking the subsequent "last index ID" requests.

This all doesn't make much sense. But this branch can be used to investigate the problem further.

Note that it was the main cause of the failing tests on master.

@icewind1991 @bantu @schiesbn @nickvergessen @bartv2 @DeepDiver1975