Fold req.htt.host to lowercase by default.

bin/varnishd/builtin.vcl

@@ -35,6 +35,9 @@ vcl 4.0;
 # Client side
 
 sub vcl_recv {
+    if (req.http.host) {
+        set req.http.host = req.http.host.lower();
+    }
     if (req.method == "PRI") {
         /* This will never happen in properly formed traffic (see: RFC7540) */
         return (synth(405));

bin/varnishtest/tests/u00010.vtc

@@ -20,7 +20,7 @@ client c1 {
 
 varnish v1 -vsl_catchup
 
-process p1 -expect-text 1 1 {list length 64}
+process p1 -expect-text 1 1 {list length 6}
 
 process p1 -writehex 0c