test_helper: ensure test client connects to valid address

You can listen on 0.0.0.0, but trying to connect to it doesn't work
well on OpenBSD.

Acked-by: Eric Wong <normalperson@yhbt.net>

test/test_helper.rb

@@ -73,6 +73,7 @@ def hit(uris)
     res = nil
 
     if u.kind_of? String
+      u = 'http://127.0.0.1:8080/' if u == 'http://0.0.0.0:8080/'
       res = Net::HTTP.get(URI.parse(u))
     else
       url = URI.parse(u[0])