circuit_has_opened() should be called for rendezvous circuit

In circuit_get_open_circ_or_launch(), for a rendezvous circuit, we directly called rend_client_rendcirc_has_opened() but I think circuit_has_opened() should be prefered here which then use a specialized function for each circuit purpose. Also, it fires a controller event where the former did not.

Side effect is that connection_ap_attach_pending() is called right after but I don't think it affects anything here but that needs review of course.