Updated openstack/openstack
Project: openstack/taskflow  e707be4f34e135381e9acbfdc3256b8b46e40ea7

Cache immutable visible scopes in the runtime component

Instead of recalculating/rewalking over the visible scopes
of atoms just calculate the scope once and cache it (as it
currently does not change at runtime) and return the cached
tuple instead to avoid the needless recreation whenever a
scope is requested for a given atom.

Change-Id: I47d24054c63e8620d26e7ade4baa239295daed0a