MB-12315: generate StreamEnd.

When a bucket crashes at go-couchbase, the channel is closed, there by KVData
should publish StreamEnd to downstream.

Change-Id: I713bb41676e95c7c16ad2edd0f8046468b0131bf
Reviewed-on: http://review.couchbase.org/42467
Reviewed-by: John Liang <johliang00@gmail.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>