Current update fails with HTTP 500 when trying to update a bound Neutron
port. Remove the binding before update and restore it during update.
For nodes in "active" state (or with instance_uuid assigned) only allow
such update in maintenance mode. This is not a breaking change, as previously
it did not work at all.
The cherry-pick has a small modification:
changed neutron.get_client to _build_client as get_client appeared in Newton.
Change-Id: I356fc0eb3702eb16b7f8e675ea416473c65af7e3
Closes-Bug: #1611744
(cherry picked from commit f4ff926ab1)
da07c91dc3