CBQE-0: print UI logs if add_node failed

Change-Id: I191a19d39ca04d29452c64acb1e020ec1c1e1c7e
Reviewed-on: http://review.couchbase.org/35357
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>