Allow disabling security groups

For some use cases it might be needed to disable security groups.
For example best DPDK performance can be achieved only with disabled
security groups.

Change-Id: I067fa230c0cc5f8042bc405249f99e09250893ec
diff --git a/metadata/service/compute/single.yml b/metadata/service/compute/single.yml
index e1196b2..3422e39 100644
--- a/metadata/service/compute/single.yml
+++ b/metadata/service/compute/single.yml
@@ -17,6 +17,7 @@
       local_ip: ${_param:tenant_address}
       dvr: false
       external_access: false
+      security_groups_enabled: true
       metadata:
         host: ${_param:cluster_vip_address}
         password: ${_param:metadata_password}