* Rename const for topology.../zone
* Rename const for topology.../region
* Rename const for failure-domain.../zone
* Rename const for failure-domain.../region
* Restore old names for compat
This commit transforms the next() function of the scheduler node
tree into a listNodes() function that directly returns a list of
nodes, going through the zones in a round-robin fashion. This
removes the flawed logic of the next() function.
When create fake data for the nodeTree unittests, The 'append' is invoked
on the common fake data set. That makes the unittests is running with unexpected
fake data after that.
