Fix service type for Magnum resources
Fix service type for Magnum resources

The Magnum service type was changed in
https://review.openstack.org/#/c/319300
This updates the MagnumClientPlugin with
these changes.

Change-Id: I96a69d7fde8b84f93244c5303fa5d02e76fe7e42
Closes-Bug: #1594963

openstack/heat,cwolferh/heat-scratch,noironetworks/heat,cwolferh/heat-scratch,noironetworks/heat,openstack/heat