Cause: when using HA routers, when port binding is updated, Neutron API server attempted to reallocate fixed IPs for the port regardless that they were not touched by API consumer. This could trigger a race condition with another thread updating the port. Consequence: sometimes the race condition resulted in legit IP addresses being erroneously deallocated for affected ports. Fix: L3 HA port update code no longer attempts to update fixed IPs when updating router bindings, which avoids the race condition. Result: no IP addresses are erroneously deallocated from ports when their router bindings change even when other API consumers update the port too.