LUSetNodeParams/LUOobCommand respect offline/powered

This patch makes sure we cross verify the state the node is
in with our view:

power off -> Node has to be set offline
modify -O no -> Node has to be powered

Signed-off-by: René Nussbaumer <rn@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>