Patch ports are not created while using ODL for L2 handling and Neutron L3-agent to handle L3 in legacy netvirt

ODL version: Beryllium SR3
openstack version: Mitaka

issue scenario:
Instance in Openstack to use multiple external provider networks.
we are using ODL for L2 handling and Neutron L3-agent to handle L3.
because ODL does not support Multiple external network.
in this scenario we are expecting ODL to create patch port in br-int and br-ex during external network creation.Also ODL controller to wirte the flows which forward the traffic via patch ports when the user attach the gateway and interface to the router.

The same use case with openvswitch as L2 and Neutron L3-agent to handle L3.Openvswitch driver creating patch ports also writing flows(converting local VLAN to provider VLAN and sending the packets to respective interface) in br-int and br-ex to forward the packets to external Network host.

steps to reproduce the Bug:

1.in devstack local.conf file make changes to create vlan network.
Q_ML2_PLUGIN_TYPE_DRIVERS=vlan,gre,vxlan,flat
[ovs]
local_ip=$HOST_IP
bridge_mappings = physnet1:br-ex
[ml2_type_vlan]
network_vlan_ranges=physnet1:171:172

2.comment "ovsdb.l3.fwd.enabled=yes" in "etc/custom.properties" file.
3.start the controller and install "odl-ovsdb-openstack".
4.Run the devstack "./stack.sh"
5.After stack UP create br-ex and add port to it.
"sudo ovs-vsctl add-br br-ex"
"sudo ovs-vsctl add-port br-ex ens35"
6.now create internal network and VM'scenario
7.Create two VLAN provider network.
8.Create two Routers and attach Gateway.
9.Associate floating IP try to reach external Gateway from the openstack VM instance.