Fix for the small error handling problem

when handleResponse is called, currentCommand is already 0xff

Change-Id: I090b1f9787935e280b88e832aed3e885f4f27c0d
Reviewed-on: http://review.couchbase.org/30225
Tested-by: Artem Stemkovski <artem@couchbase.com>
Reviewed-by: Chiyoung Seo <chiyoung@couchbase.com>
Tested-by: Chiyoung Seo <chiyoung@couchbase.com>