Ensures port is not created when database exception occurs

Fixes bug 1064261

The port creation code did not correctly treat a database error. That is,
if there was an exception the port would be created and an error returned
to the client.

Change-Id: I6cf36d1c641b46716afb16f228b8daa631099a5d

quantum/db/db_base_plugin_v2.py

@@ -1160,9 +1160,8 @@ def create_port(self, context, port):
                                   device_owner=p['device_owner'])
             context.session.add(port)
 
-        # Update the allocated IP's
-        if ips:
-            with context.session.begin(subtransactions=True):
+            # Update the allocated IP's
+            if ips:
                 for ip in ips:
                     LOG.debug("Allocated IP %s (%s/%s/%s)", ip['ip_address'],
                               port['network_id'], ip['subnet_id'], port.id)

quantum/tests/unit/test_db_plugin.py

@@ -1196,6 +1196,19 @@ def test_requested_split(self):
                 for p in ports_to_delete:
                     self._delete('ports', p['port']['id'])
 
+    def test_duplicate_ips(self):
+        fmt = 'json'
+        with self.subnet() as subnet:
+            # Allocate specific IP
+            kwargs = {"fixed_ips": [{'subnet_id': subnet['subnet']['id'],
+                                     'ip_address': '10.0.0.5'},
+                                    {'subnet_id': subnet['subnet']['id'],
+                                     'ip_address': '10.0.0.5'}]}
+            net_id = subnet['subnet']['network_id']
+            res = self._create_port(fmt, net_id=net_id, **kwargs)
+            port2 = self.deserialize(fmt, res)
+            self.assertEquals(res.status_int, 500)
+
     def test_requested_ips_only(self):
         fmt = 'json'
         with self.subnet() as subnet: