[ovn] Handle ovn central options

Since ovs 2.8 remote ports of NB/SB are closed by default,
so get options from pillar to open required ports.

Change-Id: I4b4437a35ec8719113757a524f429b5d7b3cd28e
diff --git a/README.rst b/README.rst
index 5d21c9e..570558c 100644
--- a/README.rst
+++ b/README.rst
@@ -733,6 +733,9 @@
             ovn:
               driver: ovn
           tenant_network_types: "geneve,flat"
+        ovn_ctl_opts:
+          db-nb-create-insecure-remote: 'yes'
+          db-sb-create-insecure-remote: 'yes'
 
 Compute node: