Remove unused create_image of Nova v2 API

There are two create_image methods for Nova v2 API, but the one of
images_client.py only is used in most cases.
This patch removes the unused create_image of servers_client.py.

Change-Id: Icd457b6693c076c5c8b9d48bb88da162161c9a1a
diff --git a/tempest/api/compute/test_authorization.py b/tempest/api/compute/test_authorization.py
index 7f909d7..c87f24e 100644
--- a/tempest/api/compute/test_authorization.py
+++ b/tempest/api/compute/test_authorization.py
@@ -60,7 +60,7 @@
         resp, cls.server = cls.client.get_server(server['id'])
 
         name = data_utils.rand_name('image')
-        resp, body = cls.client.create_image(server['id'], name)
+        resp, body = cls.images_client.create_image(server['id'], name)
         image_id = data_utils.parse_image_id(resp['location'])
         cls.images_client.wait_for_image_status(image_id, 'ACTIVE')
         resp, cls.image = cls.images_client.get_image(image_id)
diff --git a/tempest/services/compute/json/servers_client.py b/tempest/services/compute/json/servers_client.py
index d6705db..cdce8d7 100644
--- a/tempest/services/compute/json/servers_client.py
+++ b/tempest/services/compute/json/servers_client.py
@@ -260,10 +260,6 @@
         """Reverts a server back to its original flavor."""
         return self.action(server_id, 'revertResize', None, **kwargs)
 
-    def create_image(self, server_id, name):
-        """Creates an image of the given server."""
-        return self.action(server_id, 'createImage', None, name=name)
-
     def list_server_metadata(self, server_id):
         resp, body = self.get("servers/%s/metadata" % str(server_id))
         body = json.loads(body)