Implement update for neutron port resources

This change allows any updatable properties to be updated
on an existing port without replacement. Documentation
is limited on what properties are updatable, so discovery
was manual. Unlike other neutron resources, port name is not
updateable without replacement.

Change-Id: I7845702e14baab595363d57bcf6128e45ffdd789
Closes-Bug: #1241553
Merge "Implement update for neutron port resources"