Don't cancel http_request_t if lcb function fails

http_request_t is only valid if make_http_request itself does not return
an error

Change-Id: Idabf82e1707c0e64df9f83d7932c2ae0687e08df
Reviewed-on: http://review.couchbase.org/27489
Reviewed-by: Mark Nunberg <mnunberg@haskalah.org>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>