In VectorClockMongoDTestPrimary setup the clusterRole is set to ShardServer and the replica set member state to primary. Such global state should be cleared in the tearDown because subsequent tests can depend on it.

For instance, the gossipOut test is currently working "by hazard" because tests based on VectorClockMongoDTest fixture are always executed before VectorClockMongoDTestPrimary ones. Changing such order - e.g. by changing fixtures alphabetical order - would cause the test to break because the result depends on clusterRole.

PS: this ticket is probably a good reason to push for a randomization of unit tests order.