Updated openstack/openstack
Project: openstack/taskflow  41e5a769a46adfc4f0acccb763938b6a6e075c4f

Relax the linear flow symbol constraints

In order to make it possible to have a symbol
tree we need to relax and remove the constraints
that are being imposed by the linear constraints
and later move those constraint checks and validations
into the engines compilation stage.

Part of blueprint taskflow-improved-scoping

Change-Id: I6efdc821ff991e83572d89f56be5c678d007f9f8