Adds Designate server-list scenario

This submission adds method to
rally/benchmark/scenarios/designate/basic.py

1)def list_servers

Added configuration files for server operations under
samples/tasks/scenarios/designate

1) list-servers.json
2) list-servers.yaml
Also, added unittests to test_basic.py under
tests/unit/benchmark/scenarios/designate

Change-Id: I948f5e0c8beca963a9d6f1d388ea0410f2d107e3

rally-jobs/rally-designate.yaml

@@ -100,3 +100,18 @@
       sla:
         failure_rate:
           max: 0
+
+  DesignateBasic.list_servers:
+    -
+      runner:
+        type: "constant"
+        times: 4
+        concurrency: 2
+      context:
+        users:
+          tenants: 2
+          users_per_tenant: 2
+      sla:
+        failure_rate:
+          max: 0
+

rally/benchmark/scenarios/designate/basic.py

@@ -162,3 +162,14 @@ class DesignateBasic(utils.DesignateScenario):
         """
         server = self._create_server()
         self._delete_server(server["id"])
+
+    @validation.required_services(consts.Service.DESIGNATE)
+    @validation.required_openstack(admin=True)
+    @base.scenario(context={"cleanup": ["designate"]})
+    def list_servers(self):
+        """List Designate servers.
+
+        This simple scenario tests the designate server-list command by listing
+        all the servers.
+        """
+        self._list_servers()

samples/tasks/scenarios/designate/list-servers.json

@@ -0,0 +1,17 @@
+{
+    "DesignateBasic.list_servers": [
+        {
+            "runner": {
+                "type": "constant",
+                "times": 3,
+                "concurrency": 2
+            },
+            "context": {
+                "users": {
+                    "tenants": 2,
+                    "users_per_tenant": 2
+                }
+            }
+        }
+    ]
+}

samples/tasks/scenarios/designate/list-servers.yaml

@@ -0,0 +1,11 @@
+---
+  DesignateBasic.list_servers:
+    -
+      runner:
+        type: "constant"
+        times: 3
+        concurrency: 2
+      context:
+        users:
+          tenants: 2
+          users_per_tenant: 2

tests/unit/benchmark/scenarios/designate/test_basic.py

@@ -134,3 +134,11 @@ class DesignateBasicTestCase(test.TestCase):
 
         mock_create.assert_called_once_with()
         mock_delete.assert_called_once_with("123")
+
+    @mock.patch(DESIGNATE_BASIC + "._list_servers")
+    def test_list_servers(self, mock_list):
+        scenario = basic.DesignateBasic()
+
+        # Default options
+        scenario.list_servers()
+        mock_list.assert_called_once_with()