MB-9821: Add takeover stream logic

The change adds two more states to the producer stream state
machine to allow a producer to properly hand off a vbucket to
another node.

Change-Id: Ia7925442b9f8cb984639b331ae642d90c9ef94a0
Reviewed-on: http://review.couchbase.org/31515
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>