Explicitly specify `zoneid` in CloudStack's `associateIpAddress` call (#4995)

Generally speaking, this must be harmless since the IP address
and the virtual machine need to be deployed to the same zone.

builder/cloudstack/step_configure_networking.go

@@ -74,6 +74,8 @@ func (s *stepSetupNetworking) Run(state multistep.StateBag) multistep.StepAction
 			p.SetNetworkid(network.Id)
 		}
 
+		p.SetZoneid(config.Zone)
+
 		// Associate a new public IP address.
 		ipAddr, err := client.Address.AssociateIpAddress(p)
 		if err != nil {