Always use a fixed address when attaching a floating IP to a server

When using Neutron, if the caller didn't specify a fixed_address when
assigning a floating IP to a server, automatically pick the fist IPv4 address
assigned to the fist port of the server.

This should fix the DreamHost use case: DH uses Neutron and automatically
assigns an IPv4 and an IPv6 fixed address. Even if it doesn't make sense to
attach a floating IPv4 address to a fixed IPv6 address, OpenStack returns an
error if we don't specify a fixed address when attacking a floating IP to a
server port when multiple IPs assigned to that port.

Change-Id: I4b91bf29366c4d8b5277d0d97cd9571770252961

shade/__init__.py

@@ -2092,6 +2092,15 @@ def _neutron_attach_ip_to_server(self, server_id, floating_ip_id,
             port = None
             if ports and fixed_address is None:
                 port = ports[0]
+                # Select the first available IPv4 address
+                for address in port.get('fixed_ips', list()):
+                    if _utils.is_ipv4(address['ip_address']):
+                        fixed_address = address['ip_address']
+                        break
+                if fixed_address is None:
+                    raise OpenStackCloudException(
+                        "unable to find a suitable IPv4 address for server "
+                        "{0}".format(server_id))
             elif ports:
                 # unfortunately a port can have more than one fixed IP:
                 # we can't use the search_ports filtering for fixed_address as

shade/tests/unit/test_floating_ip_neutron.py

@@ -290,7 +290,9 @@ def test_attach_ip_to_server(
             floatingip=self.mock_floating_ip_new_rep['floatingip']['id'],
             body={
                 'floatingip': {
-                    'port_id': self.mock_search_ports_rep[0]['id']
+                    'port_id': self.mock_search_ports_rep[0]['id'],
+                    'fixed_ip_address': self.mock_search_ports_rep[0][
+                        'fixed_ips'][0]['ip_address']
                 }
             }
         )