Remove max_nested_cluster_depth config option
Remove max_nested_cluster_depth config option

We are now suspending our support to nested clusters. This patch removes
the configuration option related to this feature.

Change-Id: Ia0476e0c92429d20a003b5b9b2b5e9fb6c7d5000

stackforge/senlin,openstack/senlin,tengqm/senlin-container,stackforge/senlin,tengqm/senlin-container,openstack/senlin,openstack/senlin