Networking URL construction no longer adds /v2.0

Because it's already handled by the ResourceBase that's set up when you
acquire a client.
diff --git a/openstack/networking/v2/subnets/urls_tests.go b/openstack/networking/v2/subnets/urls_tests.go
index b04b432..aeeddf3 100644
--- a/openstack/networking/v2/subnets/urls_tests.go
+++ b/openstack/networking/v2/subnets/urls_tests.go
@@ -10,7 +10,7 @@
 const endpoint = "http://localhost:57909/"
 
 func endpointClient() *gophercloud.ServiceClient {
-	return &gophercloud.ServiceClient{Endpoint: endpoint}
+	return &gophercloud.ServiceClient{Endpoint: endpoint, ResourceBase: endpoint + "v2.0/"}
 }
 
 func TestListURL(t *testing.T) {