minor and cosmetic simplification of the hex test

src/tests/hex.vtc

@@ -2,11 +2,10 @@
 
 varnishtest "hex encode and decode"
 
-server s1 {} -start
-
-varnish v1 -vcl+backend {
+varnish v1 -vcl {
 	import convert from "${vmod_topbuild}/src/.libs/libvmod_convert.so";
 	import ${vmod_std};
+	backend b { .host = "${bad_ip}"; }
 
 	sub vcl_recv {
 	  return(synth(200));
@@ -160,8 +159,9 @@ client c1 {
 	expect resp.http.decmanypieces == "foo bar baz quux"
 } -run
 
-varnish v1 -vcl+backend {
+varnish v1 -vcl {
 	import convert from "${vmod_topbuild}/src/.libs/libvmod_convert.so";
+	backend b { .host = "${bad_ip}"; }
 
 	sub vcl_recv {
 	  return(synth(200));