Adding GetConfig operation for Rackspace provider
diff --git a/rackspace/db/v1/instances/urls.go b/rackspace/db/v1/instances/urls.go
index bb6edf2..c0c1bad 100644
--- a/rackspace/db/v1/instances/urls.go
+++ b/rackspace/db/v1/instances/urls.go
@@ -9,3 +9,7 @@
 func createURL(c *gophercloud.ServiceClient) string {
 	return baseURL(c)
 }
+
+func configURL(c *gophercloud.ServiceClient) string {
+	return c.ServiceURL("instances", id, "configuration")
+}