Fix server action resource call

Currently, action resource call of nova server doesn't work
correctly in case where action API doesn't have response body.
This patch fixes this issue.

Change-Id: I016f74507f7d5b5792c77879969bdc271c25f829
Closes-Bug: #1528145

openstack/compute/v2/server.py

@@ -86,16 +86,12 @@ class Server(resource.Resource):
 
         return body
 
-    def action(self, session, body, has_response=False):
+    def action(self, session, body):
         """Preform server actions given the message body."""
         url = utils.urljoin(self.base_path, self.id, 'action')
-        if has_response:
-            resp = session.post(url, endpoint_filter=self.service, json=body)
-        else:
-            headers = {'Accept': ''}
-            resp = session.post(
-                url, endpoint_filter=self.service, json=body, headers=headers)
-        return resp.json()
+        headers = {'Accept': ''}
+        session.post(
+            url, endpoint_filter=self.service, json=body, headers=headers)
 
     def change_password(self, session, new_password):
         """Change the administrator password to the given password."""

openstack/tests/unit/compute/v2/test_server.py

@@ -45,7 +45,7 @@ class TestServer(testtools.TestCase):
     def setUp(self):
         super(TestServer, self).setUp()
         self.resp = mock.Mock()
-        self.resp.body = ''
+        self.resp.body = None
         self.resp.json = mock.Mock(return_value=self.resp.body)
         self.sess = mock.Mock()
         self.sess.post = mock.Mock(return_value=self.resp)