Set dummy savepoint path during last-state upgrade

Currently the operator always sets the savepoint path even if last-state (HA metadata) must be used. 

This can be misleading to users as the set savepoint path normally should never take effect and can actually lead to incorrect state restored if the HA metadata is deleted by the user at the wrong moment.

To avoid this we can set an explicit dummy savepoint path which will prevent restoring from it accidentally.