Add docker to image_schema on glance v2 cli

Add docker to v2 image_schema
Add docker to v2 unit tests

This is related to following glance api extension.
  https://review.openstack.org/#/c/249282/

Co-Authored-By: Kairat Kushaev <kkushaev@mirantis.com>

Closes-Bug: #1519402
Change-Id: Ia015f027788b49c1b0002fb3e3a93ac825854596

glanceclient/tests/unit/v2/fixtures.py

@@ -112,7 +112,8 @@ schema_fixture = {
                 "aki",
                 "bare",
                 "ovf",
-                "ova"
+                "ova",
+                "docker"
             ],
             "type": [
                 "null",

glanceclient/tests/unit/v2/test_shell_v2.py

@@ -40,7 +40,8 @@ def schema_args(schema_getter, omit=None):
     my_schema_getter = lambda: {
         'properties': {
             'container_format': {
-                'enum': [None, 'ami', 'ari', 'aki', 'bare', 'ovf', 'ova'],
+                'enum': [None, 'ami', 'ari', 'aki', 'bare', 'ovf', 'ova',
+                         'docker'],
                 'type': 'string',
                 'description': 'Format of the container'},
             'disk_format': {

glanceclient/v2/image_schema.py

@@ -44,7 +44,8 @@ _BASE_SCHEMA = {
                 "aki",
                 "bare",
                 "ovf",
-                "ova"
+                "ova",
+                "docker"
             ],
             "type": "string",
             "description": "Format of the container"