Set HTTP X-Forward-For option as default in HAProxy config.

This change adds the option forwardfor field under
frontend section in haproxy config file for HTTP and
HTTPS protocols. This will make sure that client's IP
is always forwarded to server in request header.

Change-Id: I8bc9bc1e70285e5a4f1b3eba2ceff51d7229d45d
Closes-Bug: #1485782

src/vnsw/agent/oper/loadbalancer_haproxy.cc

@@ -126,6 +126,12 @@ void LoadbalancerHaproxy::GenerateFrontend(
         *out << string(4, ' ')
              << "maxconn " << vip.connection_limit << endl;
     }
+
+    if (vip.protocol == "HTTP" || vip.protocol == "HTTPS") {
+        *out << string(4, ' ')
+             << "option forwardfor" << endl;
+    }
+
     *out << endl;
 }