Avoid creating auto-tunnels for VLAN tenant networks

Setup:
In a Multi-node setup with a controller node (running dhcp-agent) and one or more compute nodes.

Steps:
1. Create a Neutron Router.
2. Create a tenant VLAN network.
3. Create an IPv4 subnet in the tenant VLAN network.
4. Associate the subnet to the Neutron router.
5. Spawn a VM on one of the compute nodes.

Observations: A VxLAN tunnel is setup between the Controller node (running dhcp-agent) and Compute node (hosting the VM).
This is creating issues in VM acquiring the IP address.

Expected behavior: When using a VLAN tenant network, auto-tunnel code of Netvirt should NOT be creating any VxLAN tunnels.