CBQE-0: Fix _Thread__stop() is func for threading.Thread object

Change-Id: I037c9ddf29720c9de13869d0637aa659d07f04dc
Reviewed-on: http://review.couchbase.org/35646
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Reviewed-by: Parag Agarwal <agarwal.parag@gmail.com>
Tested-by: Parag Agarwal <agarwal.parag@gmail.com>