Feature/filestorage sharenetworks update (#126)

* sfs: Add update for share networks

* sfs: Add acceptance tests for share network Update

* sfs: Add possiblity to update the network for share network

* sfs: Improve share network Update unit tests

* sfs: Improve share network Update acceptance tests
diff --git a/openstack/sharedfilesystems/v2/sharenetworks/results.go b/openstack/sharedfilesystems/v2/sharenetworks/results.go
index ce2b00b..1eb64bc 100644
--- a/openstack/sharedfilesystems/v2/sharenetworks/results.go
+++ b/openstack/sharedfilesystems/v2/sharenetworks/results.go
@@ -142,3 +142,8 @@
 type GetResult struct {
 	commonResult
 }
+
+// UpdateResult contains the response body and error from an Update request.
+type UpdateResult struct {
+	commonResult
+}