Rename changes-since test sample file

In the past, we only have changes-since filter, we called it as
timestamp-filter, but now we will add a changes-before filter,
the timestamp-filter is not clear anymore.

In this patch, we rename timestamp to changes-since.

Change-Id: Ieee912e197d17a5ffca7460f3b977316cd21813e
blueprint: support-to-query-nova-resources-filter-by-changes-before

nova/tests/functional/api_sample_tests/test_instance_actions.py

@@ -110,13 +110,13 @@ class ServerActionsV258SampleJsonTest(ServerActionsV251AdminSampleJsonTest):
         self._verify_response('instance-actions-list-with-marker-resp',
                               self._get_subs(), response, 200)
 
-    def test_instance_actions_with_timestamp_filter(self):
+    def test_instance_actions_with_changes_since(self):
         stop_action_time = self.action_stop['start_time']
         response = self._do_get(
             'servers/%s/os-instance-actions'
             '?changes-since=%s' % (self.uuid, stop_action_time))
         self._verify_response(
-            'instance-actions-list-with-timestamp-filter',
+            'instance-actions-list-with-changes-since',
             self._get_subs(), response, 200)
 
 

nova/tests/functional/api_sample_tests/test_migrations.py

@@ -285,10 +285,10 @@ class MigrationsSamplesJsonTestV2_59(MigrationsSamplesJsonTestV2_23):
             {"instance_1": INSTANCE_UUID_1, "instance_2": INSTANCE_UUID_2},
             response, 200)
 
-    def test_get_migrations_with_timestamp_filter(self):
+    def test_get_migrations_with_changes_since(self):
         response = self._do_get(
             'os-migrations?changes-since=2016-06-23T13:42:01.000000')
         self.assertEqual(200, response.status_code)
         self._verify_response(
-            'migrations-get-with-timestamp-filter',
+            'migrations-get-with-changes-since',
             {"instance_2": INSTANCE_UUID_2}, response, 200)