Implement VDI.{activate,deactivate}
Implement VDI.{activate,deactivate}

Leave both as no-ops for now.

Signed-off-by: David Scott <63c9eb0ea83039690fefa11afe17873ba8278a56@eu.citrix.com>

franciozzy/ffs,xapi-project/ffs,djs55/ffs,robertbreker/ffs