SERVER-18867 no longer requires individual storage engines to implement their own registerChange logic by moving this logic up to the RecoveryUnit class. The ephemeralForTest storage engine must still implement its own registerChange logic because the generic RecoveryUnit registerChange logic added as of SERVER-18867 has an invariant that fails on ephemeralForTest.

ephemeralForTest should be modified to use the generic RecoveryUnit registerChange logic.