Added one TODO item about scaling policy
Added one TODO item about scaling policy

Just got a requirement: scaling a cluster to existing nodes instead of
creating new nodes. This won't be a complicated policy.

Change-Id: I4a284832fcd9ceab863809271e06b925da8d0b8c

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