Fix up port test

It seems like glibc's getaddrinfo is entirely happy to accept 70000 as
a valid port, so use something that's not a valid service name so make
check still works.


git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@3293 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishtest/tests/v00002.vtc

@@ -122,7 +122,7 @@ varnish v1 -badvcl {
 }
 
 varnish v1 -badvcl {
-	backend b1 { .host = "127.0.0.1"; .port = "70000"; }
+	backend b1 { .host = "127.0.0.1"; .port = "////"; }
 }
 
 varnish v1 -badvcl {