Table 21 entry not getting removed after removing vpn footprint from Switch

After deleting all the VMs from switch i.e removing the VPN footprint, Table 21 entry are not getting removed.

Steps to reproduce:
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1. Create 2 VMs on all switch (tested with 3 switch)
2. Associate Network to Neutron Router
3. Associate Neutron Router to Neutron BgpVpn
4. Define ECMP routes on router , pointing to 2 VM on Switch1 and 2 Vm on switch2
5. verify the flows on all switch
6. Delete all VMs on Switch3
As all VMs are deleted , Vpn footprint has removed fron Switch3. So All Table 21 entries should also get removed.