Close native transport port before hint transfer during decommission

New hints can be generated on a node when it's decommissioning which is a problem if the node has already started hint transfer because any hints that come in after the transfer has begun will remain on-disk and not be transferred to a peer.

You can work around this problem by manually closing the native transport port before starting the decommission with nodetool disablebinary but it feels like something we might want to do automatically.