Use overlay2 driver by default

Also print deprecation message for devicemapper and overlay.

Change-Id: Idff7f518485528da45430ae85a1580ed9d306330

magnumclient/osc/v1/cluster_templates.py

@@ -151,9 +151,9 @@ class CreateClusterTemplate(command.ShowOne):
             '--docker-storage-driver',
             dest='docker_storage_driver',
             metavar='<docker-storage-driver>',
-            default='devicemapper',
+            default='overlay2',
             help=_('Select a docker storage driver. Supported: devicemapper, '
-                   'overlay. Default: devicemapper'))
+                   'overlay, overlay2. Default: overlay2'))
         parser.add_argument(
             '--http-proxy',
             dest='http_proxy',
@@ -278,6 +278,12 @@ class CreateClusterTemplate(command.ShowOne):
         elif len(parsed_args.floating_ip_enabled) == 1:
             args['floating_ip_enabled'] = parsed_args.floating_ip_enabled[0]
 
+        deprecated = ['devicemapper', 'overlay']
+        if args['docker_storage_driver'] in deprecated:
+            print("WARNING: Docker storage drivers %s are deprecated and will "
+                  "be removed in a future release. Use overlay2 instead." %
+                  deprecated)
+
         ct = mag_client.cluster_templates.create(**args)
         print("Request to create cluster template %s accepted"
               % parsed_args.name)

magnumclient/tests/osc/unit/v1/test_cluster_templates.py

@@ -28,7 +28,7 @@ class TestClusterTemplate(magnum_fakes.TestMagnumClientOSCV1):
     default_create_args = {
         'coe': 'kubernetes',
         'dns_nameserver': '8.8.8.8',
-        'docker_storage_driver': 'devicemapper',
+        'docker_storage_driver': 'overlay2',
         'docker_volume_size': None,
         'external_network_id': 'public',
         'fixed_network': None,