=act #3853 Fix consistent hashing group inconsistency

* It did not use the toString (including full address of destination) of the
  node entries, instead it used the hashCode which always included the self
  address
* This was a regression in 2.3, it is correct in 2.2.3
Merge pull request #1978 from akka/wip-3853-consistent-hashing-group-patriknw

=act #3853 Fix consistent hashing group inconsistency