Fix updating for OS::Neutron::Port resource

Updating of port resource should not lead to removing ip address.
This patch includes next changes:
- Fix update behavior for Port resource.
- Using properties names instead of constant names.
- New test was added for port create/update actions.

Change-Id: Iff73aaaa433ac56515a931f83ad201d15fca2bd8
Closes-Bug: #1343166
Merge "Fix updating for OS::Neutron::Port resource"