core: Add VdcActionType tests

Added tests to:
- Validate that every command values is unique
- Validate that every command type in VdcActionType corresponds to an
  existing command class

Change-Id: I53b51b359e14e2f1ebb6e518846f1cf00c8bbe6b
Signed-off-by: Tal Nisan <tnisan@redhat.com>