IP allocation was initially deffered due to lack of binding
information. On port update the with both `mac_address` and
`binding_host_id`` in the request 'fixed_ips: ' was
appended to the new_port data. This caused the check for
fixed_ips_requested to return True, which in turn cause
deferred_ip_allocation to evaluates False.
Only set the new_port default fixed_ips to original_ips if
the original port had fixed_ips.