Change POST and DELETE return codes (kytos#22)

* Change POST and DELETE return codes

POST and DELETE methods were returning 200 but
should return 202 when the NApp sucessfully send
the flows to the switches.
Fixes kytos#20 and kytos#21.

* Modify tests to reflect the different return codes

main.py

@@ -430,7 +430,7 @@ def _send_flow_mods_from_request(self, dpid, command, flows_dict=None):
             self._install_flows(command, flows_dict,
                                 self._get_all_switches_enabled())
 
-        return jsonify({"response": "FlowMod Messages Sent"})
+        return jsonify({"response": "FlowMod Messages Sent"}), 202
 
     def _install_flows(self, command, flows_dict, switches=[], save=True):
         """Execute all procedures to install flows in the switches.

tests/unit/test_main.py

@@ -108,7 +108,7 @@ def test_rest_add_and_delete_without_dpid(self, mock_install_flows):
             response_1 = api.post(url, json={'flows': [{"priority": 25}]})
             response_2 = api.post(url)
 
-            self.assertEqual(response_1.status_code, 200)
+            self.assertEqual(response_1.status_code, 202)
             self.assertEqual(response_2.status_code, 400)
 
         self.assertEqual(mock_install_flows.call_count, 2)
@@ -125,9 +125,9 @@ def test_rest_add_and_delete_with_dpid(self, mock_install_flows):
             response_1 = api.post(url_1, json=data)
             response_2 = api.post(url_2, json=data)
 
-            self.assertEqual(response_1.status_code, 200)
+            self.assertEqual(response_1.status_code, 202)
             if method == 'delete':
-                self.assertEqual(response_2.status_code, 200)
+                self.assertEqual(response_2.status_code, 202)
 
         self.assertEqual(mock_install_flows.call_count, 3)