Adds Magnum Container Network Model to Swarm

1. Updates network-driver API validation.
2. Updates AtomicSwarm template definition for swarm, flannel and
   labels.
3. Adds initial unit test.

Partially-Implements: blueprint extend-baymodel-net-attributes
Partially-Implements: blueprint conductor-template-net-update

Change-Id: Ia80f239bcbd29ae14de25ae3e915a49d9b9bafd1

magnum/tests/functional/common/datagen.py

@@ -49,7 +49,7 @@ def generate_random_coe():
 def generate_random_coe_dep_network_driver(coe):
     allowed_driver_types = {
         'kubernetes': ['flannel', None],
-        'swarm': ['docker', None],
+        'swarm': ['docker', 'flannel', None],
         'mesos': ['docker', None],
     }
     driver_types = allowed_driver_types[coe]