Add tests when upsert fails due to a `BulkWriteException`

[GromNaN]

I fixed some exception class name in #2770, but the test suite was passing even if the exception class in the catch block doesn't exist, proving a test is missing.

mongodb-odm/lib/Doctrine/ODM/MongoDB/Persisters/DocumentPersister.php

Lines 264 to 274 in 9cc8291

	foreach ($this->queuedUpserts as $oid => $document) {
	try {
	$this->executeUpsert($document, $options);
	$this->handleCollections($document, $options);
	unset($this->queuedUpserts[$oid]);
	} catch (BulkWriteException $e) {
	unset($this->queuedUpserts[$oid]);
	throw $e;
	}
	}

On a quick research, this piece of code was added by 8251bb9