OGM-315 OneToOneTest does not completly clean the datastore at the end

https://hibernate.atlassian.net/browse/OGM-315

OneToOneTest#testBidirectionalManyToOne is sometimes executed before OneToOneTest#testUnidirectionalManyToOne.

Because one entity is not deleted there is sometimes a failure when the method checkCleanCache(); is called in  testUnidirectionalManyToOne

I'm starting to think that this method should be called after every test.