sheep: set LOCK_VDI/GET_VDI_INFO/RELEASE_VDI as local type

There is no need to broadcast these operations for now. Set them as local type
will reduce the network traffic.

Signed-off-by: Liu Yuan <tailai.ly@taobao.com>
Signed-off-by: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>