FIP attached to fixed-ip remains even when port is update with other fixed-ips

When we create a port on a network and attach fip to the port with let's say fixed-ip IP1
Then we attach FIP to the port. Now update the port with other fixed-ips other than IP1, the port gets updated but the FIP is not and the FIP is still attached to the port with fixed-ip IP1.
Neutron should block updation of port if that Fip is already attached to the vport with fixed-ip.

Step-by-step reproduction steps:
neutron router-create router
neutron net-create private
neutron subnet-create private 10.0.0.0/24 --name private_subnet
neutron router-interface-add router private_subnet
neutron net-create public --router:external=True
neutron subnet-create public 192.124.0.0/24 --name public_subnet --enable_dhcp=False --allocation-pool start=192.124.0.5,end=192.124.0.250 --gateway=192.124.0.1
neutron router-gateway-set router public
neutron port-create private --fixed-ip subnet_id=<private_subnet-id>,ip_address=10.0.0.10 --name port1

neutron floatingip-create public --name fip
neutron floatingip-associate fip port1
neutron port-update port1 --fixed-ip subnet_id=<private_subnet-id>,ip_address=10.0.0.11 --fixed-ip subnet_id=<private_subnet-id>,ip_address=10.0.0.12 --fixed-ip subnet_id=<private_subnet-id>,ip_address=10.0.0.13

neutron floatingip-show fip1 -> will show the fip is associate with port with fixed-ip 10.0.0.10 which even doesn

Expected output:
I think we should fail at a point when we update a port with fixed-ips, if fixed-ip doesn't contain original fixed-ip and fip is attached to it.

Actual output: did the system silently fail (in this case log traces are useful)?
https://pastebin.com/J2Yv947c

* Version:
  ** stable/ocata, stable/pike etc...
  ** Ubuntu16.04
  ** DevStack

Perceived severity: Medium