Orphaned vpn-portip-to-port entry after deleting VM

The vpn-portip-to-port entry associates with VM remains after the VM is deleted. This might cause issue if netvirt checks for known neutron port via call to method VpnUtil.getNeutronPortFromVpnPortFixedIp.

The entry is not removed even when the router (vpn) is removed.

Version Tested: master

Reproduction Steps:

1) Create net/subnet

2) Create VM on subnet

3) Create router 

4) Add subnet to router

  The "vpn-portip-to-port" entry for the VM is added to DS:

"neutron-vpn-portip-port-data": {
  "vpn-portip-to-port": [
 

{     "mac-address": "fa:16:3e:b2:24:cb",     "port-fixedip": "10.100.1.15",     "port-name": "1f71ed40-0a96-4aad-860b-4b549dc26e41",     "subnet-ip": false,     "vpn-name": "c8f2409b-7c18-45e7-927e-e11b22279814"  }

]

5) Delete the VM (fixed IP 10.100.1.15) - The vpn-portip-to-port entry associates with the deleted VM remains in DS, even though the port with fixed IP 10.100.1.15 is gone.

6) Remove the subnet from router

7) Delete the router

The above  vpn-portip-to-port entry still exists even though the router VPN is deleted