Add os-volume_upload_image action to volumeactions (#240)

* Add os-volume_upload_image action to volumeactions

* Code updates to align with style guide
diff --git a/openstack/blockstorage/extensions/volumeactions/urls.go b/openstack/blockstorage/extensions/volumeactions/urls.go
index a172549..5efd2b2 100644
--- a/openstack/blockstorage/extensions/volumeactions/urls.go
+++ b/openstack/blockstorage/extensions/volumeactions/urls.go
@@ -14,6 +14,10 @@
 	return attachURL(c, id)
 }
 
+func uploadURL(c *gophercloud.ServiceClient, id string) string {
+	return attachURL(c, id)
+}
+
 func reserveURL(c *gophercloud.ServiceClient, id string) string {
 	return attachURL(c, id)
 }