Transform IPAddress to string when creating port

If ip address is provided when running nova boot, nova compute
will invoke neutron client to create a port. However, the ip
address parameter is an IPAddress object so neutron client will
fail to send the request to neutron server. Transform IPAddress
object to string to address this issue.

Change-Id: I858cca475748795aa2532f32bfe0f1443b30966f
Closes-Bug: #1408529

nova/network/neutronv2/api.py

@@ -257,7 +257,8 @@ class API(base_api.NetworkAPI):
         """
         try:
             if fixed_ip:
-                port_req_body['port']['fixed_ips'] = [{'ip_address': fixed_ip}]
+                port_req_body['port']['fixed_ips'] = [
+                    {'ip_address': str(fixed_ip)}]
             port_req_body['port']['network_id'] = network_id
             port_req_body['port']['admin_state_up'] = True
             port_req_body['port']['tenant_id'] = instance['project_id']

nova/tests/unit/network/test_neutronv2.py

@@ -497,8 +497,8 @@ class TestNeutronv2Base(test.TestCase):
             else:
                 request.address = fixed_ips.get(request.network_id)
                 if request.address:
-                    port_req_body['port']['fixed_ips'] = [{'ip_address':
-                                                           request.address}]
+                    port_req_body['port']['fixed_ips'] = [
+                        {'ip_address': str(request.address)}]
                 port_req_body['port']['network_id'] = request.network_id
                 port_req_body['port']['admin_state_up'] = True
                 port_req_body['port']['tenant_id'] = \