Network: Set floating ip other properties no need port argument

When I wants to set floating ip other properties, like tags, port argument is force to use.

openstack floating ip set --tag test1 bbe7ed3c-7b5e-47a8-bb79-48367c43039c
usage: openstack floating ip set [-h] --port <port>
                                 [--fixed-ip-address <ip-address>]
                                 [--qos-policy <qos-policy> | --no-qos-policy]
                                 [--tag <tag>] [--no-tag]
                                 <floating-ip>
openstack floating ip set: error: argument --port is required

This is a strange behavior, if we wants only to set tags or qos_policy_id before we assocaite the floating ip with port.