quantum_network should not default network provider type to local

It should allow the Quantum service to decide based on its configuration.

cloud/quantum_network

@@ -64,11 +64,11 @@ options:
         - Name to be assigned to the nework 
      required: true
      default: None
-   network_type:
+   provider_network_type:
      description:
-        - The type of the network to be created, gre, vlan, local.
+        - The type of the network to be created, gre, vlan, local. Available types depend on the plugin. The Quantum service decides if not specified.
      required: false
-     default: local
+     default: None
    provider_physical_network:
      description:
         - The physical network which would realize the virtual network for flat and vlan networks.
@@ -199,7 +199,12 @@ def _create_network(module, quantum):
 
     if module.params['provider_network_type'] == 'gre':
         network.pop('provider:physical_network', None)
-                
+
+    if module.params['provider_network_type'] is None:
+        network.pop('provider:network_type', None)
+        network.pop('provider:physical_network', None)
+        network.pop('provider:segmentation_id', None)
+
     try:
         net = quantum.create_network({'network':network})
     except Exception as e:
@@ -225,7 +230,7 @@ def main():
             region_name                     = dict(default=None),
             name                            = dict(required=True),
             tenant_name                     = dict(default=None),
-            provider_network_type           = dict(default='local', choices=['local', 'vlan', 'flat', 'gre']), 
+            provider_network_type           = dict(default=None, choices=['local', 'vlan', 'flat', 'gre']),
             provider_physical_network       = dict(default=None), 
             provider_segmentation_id        = dict(default=None), 
             router_external                 = dict(default=False, type='bool'),