Optionally avoid hint transfer during decommission - port from 5.0

This ticket is to port the changes already made for https://issues.apache.org/jira/browse/CASSANDRA-17808 to 4.0 and 4.1

This will allow the option to turn off the transferring of hints during decommission (specifically unbootstrap) 

This also allows the hints to be transferred at a higher rate during decommission, as the hinted_handoff_throttle is not divided by the number of nodes in the cluster for the unbootstrap process.