Wrong DGSCol status when scaling down

[dgkanatsios]

• Create a DGSCol of X replicas
• Scale it down to Y
• Notice that the AvailableReplicas shows X-1 instead of Y and that state (either DGSCol or Pod) does not show the correct value

[dgkanatsios]

After some investigation, it seems that the method inside DGSControler that controls the AvailableReplicas status is never called. This happens because:

• on scaleDown, a number of replicas is removed
• these replicas lose their owner references
• the DGSController is triggered again (because a DGS has had its status updated) but the controller's syncHandler is never called, because the updated DGS has no owner references
• so the AvailableReplicas is never updated

possible solutions

• add a PreviousDGSCol Label that gets examined on DGSUpdate. If it exists, then syncHandler is called with this label's value as key
• on decreaseReplicas method, modify somehow the DGSCol object, so that Update is called for that