Finish

Those tests check the return codes and the behavior of llhttp_finish() C API.

It should be safe to finish with cb after empty response

HTTP/1.1 200 OK

off=0 message begin
off=0 len=4 span[protocol]="HTTP"
off=4 protocol complete
off=5 len=3 span[version]="1.1"
off=8 version complete
off=13 len=2 span[status]="OK"
off=17 status complete
off=19 headers complete status=200 v=1/1 flags=0 content_length=0
off=NULL finish=1