Clear out the engine-specific data when done with a conn.
Clear out the engine-specific data when done with a conn.

Change-Id: I4005b2635f9e1f507a1edf2c57ef7e7b3a06b626
Reviewed-on: http://review.northscale.com/1970
Reviewed-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>
Tested-by: Steve Yen <ef850f73f7832052d3c6d9b5ddd3a1716d9a57f1@gmail.com>

membase/bucket_engine,couchbase/bucket_engine,membase/bucket_engine,couchbase/bucket_engine,membase/bucket_engine,membase/bucket_engine,couchbase/bucket_engine,couchbase/bucket_engine