Fix Magnum Kolla demo in contrib

Magnum demo scripts doesn't work cause compose/openstack.env
doesn't exist anymore.
* NETWORK_MANAGER check has been removed
* script has been updated to use Openstack client instead of
deprecated clients (neutron-client, glance-client).
* Magnum client calls have been adapted too.
* some enhancements (logs, variable) have been performed too.

Change-Id: I294b1876c9c7090785c0ebdd09b43843f88fb00b
Closes-Bug: #1670618