Introduce an option '--no-fixed-ip' on port create command.
If this option is specified and '--fixed-ip' is unspecified,
OSC will send a request to neutron with 'fixed_ips' as an empty
list, which will create an unaddress neutron port.
Note: The use cases of unaddress port was outlined in:
https://specs.openstack.org/openstack/neutron-specs/specs/liberty/unaddressed-port.html
(dtroyer: add Depends-On for Zuul v3 test)
Depends-On: I39e8e49243ab0bda631600715c971c55a34e2fd9
Change-Id: Ibe38598acbbcd0d353c952fc2a6fa67780762151
Closes-Bug: #1717829