core: Remove unused shutdown commands.

1. Removing unused vdc command ShutdownVdsCommand and its parameter class.
2. Removing vds command ShutdownVdsVDSCommand and its parameter class.
3. Finally remove all the their related unused references.

Change-Id: I42cb8777ea1838229e05c17cae46e75305510dc6
Signed-off-by: Maor Lipchuk <mlipchuk@redhat.com>