N1ql: update error messages

Change-Id: Iea5affd77193aeddf2874aa5587dcbb08d144fde
Reviewed-on: http://review.couchbase.org/44710
Reviewed-by: Iryna Mironava <irynamironava@yandex.ru>
Tested-by: Iryna Mironava <irynamironava@yandex.ru>