IPV6_service: IPV4 address assignment failing for VM already running with IPV6 address

Scenario:
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Validating dual stack Ipv4 and IPv6 address assignment to Neutron VM by creating the IPV6 subnet first, then spawn the VM and then creating IPV4 subnet.

1.create a IPV6 subnet in slaac mode:

neutron net-create mynet1
neutron subnet-create mynet1 2001:db8:1234::/64 --name ipv6s1 --ip-version 6 --ipv6-ra-mode slaac --ipv6-address-mode slaac
neutron router-create router1
neutron router-interface-add router1 ipv6s1

2.spawn the VM:

nova boot --flavor m1.small --image cirros-0.3.4-x86_64-uec --availability-zone nova:test-ovs --nic net-name=mynet1 vm1

3.create IPV4 subnet to the same network (also enable dhcp on ODL):

neutron subnet-create mynet1 13.0.0.0/24 --name ipv4s1 --enable-dhcp

5.reboot the VM

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VM doesn't receive dhcp offer even if we run dhcp client or reboot the VM. Also, the table 60 entry is missing.

But, if we create another VM, then both the addresses are assigned for it. The corresponding table 60 entries are also seen.

Attached logs:
1>Openstack log
2>Karaf log