Allow separate control and vhost0 IPs in contrail-vrouter-agent.conf

Add possibility to separate the control path for XMPP communication
between vrouter and contrail controllers to go over a separate network
from tenant traffic.

Change-Id: If618adcf6a06c2da3089b62d7433adac2c431acd
Closes-bug: PROD-8436
diff --git a/README.rst b/README.rst
index 1e9143d..243234f 100644
--- a/README.rst
+++ b/README.rst
@@ -624,6 +624,19 @@
         engine: kubernetes
       ...
 
+vRouter with separated control plane
+------------------------------------
+
+Separate XMPP traffic from dataplane interface.
+
+.. code-block:: yaml
+
+    opencontrail:
+      compute:
+        bind:
+          address: 172.16.0.50
+      ...
+
 Disable Contrail API authentication
 -----------------------------------