MB-11488 Fix to the memory leak in PassiveStream.

Change-Id: I657cc507b9fe86d9a120f6e7e4e35fd80e9de937
Reviewed-on: http://review.couchbase.org/38948
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>