Fix wrong type of volume attachments in FakeVolume

The volume attachments should be a list of dict, not a single dict.

Change-Id: I3cec62bcb3953e4f38f9d3dd23f3eb6ef984464c

Author: Tang Chen

openstackclient/tests/volume/v2/fakes.py

@@ -256,9 +256,10 @@ def create_one_volume(attrs={}):
                 'key' + uuid.uuid4().hex: 'val' + uuid.uuid4().hex},
             'snapshot_id': random.randint(1, 5),
             'availability_zone': 'zone' + uuid.uuid4().hex,
-            'attachments': {
+            'attachments': [{
                 'device': '/dev/' + uuid.uuid4().hex,
-                'server_id': uuid.uuid4().hex},
+                'server_id': uuid.uuid4().hex,
+            }, ],
         }
 
         # Overwrite default attributes if there are some attributes set