transaction policy interceptors must not enlist caller's connections

Instance interceptors are all after the tx interceptors. As a result, when a tx interceptor starts a new tx, ConnectionTrackingCoordinator.newTransaction is called and attempt to enroll any connection handles the CALLER has open in the new transaction. These handles are not going to be available to the called ejb so this is certainly wrong.

I think we can install a blank ConnectorInstanceContext in the CTC while the tx interceptors are traversed. The alternative would be to find some way to distinguish between container and bean managed transactions inside the tx manager.