http2/h2demo: set externalTrafficPolicy to preserve client IPs

So https://http2.golang.org/reqinfo has a RemoteAddr of the client's
actual IP address.

Change-Id: I9db52b2f451ad937d013dd78078e4228e732ffe0
Reviewed-on: https://go-review.googlesource.com/99235
Reviewed-by: David Anderson <danderson@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/http2/h2demo/service.yaml b/http2/h2demo/service.yaml
index 8e7671e..2b7d541 100644
--- a/http2/h2demo/service.yaml
+++ b/http2/h2demo/service.yaml
@@ -3,6 +3,7 @@
 metadata:
   name: h2demo
 spec:
+  externalTrafficPolicy: Local
   ports:
     - port: 80
       targetPort: 80