Fix validation for scaling

- When scaling up this takes number of free nodes and
  compare it to all nodes, that is bad.
- So always taking total amount of all nodes should be fine
  for now. We only have one overcloud, so for first deployment
  number of free nodes == number of all nodes.

Change-Id: I8b9fb589a5189b92f80e5a2fe6c5ef9c8587e062
Merge "Fix validation for scaling"