ISPN-2507 @DataRehashed event is not triggered

https://issues.jboss.org/browse/ISPN-2507
https://issues.jboss.org/browse/ISPN-2401

I fixed ISPN-2401 as well, because it needed the same approach as notifying
the listeners of the start and end of rebalancing at the right time.

I added the consistent hash to the DataRehashedEvent, which should be
backwards compatible, because user code is not supposed to implement it.