CP-10203: XenAPI: api call for RDP on/off request
Code update to address the review comments.

Signed-off-by: Hui Zhang <hui.zhang@citrix.com>
CP-10203: XenAPI: api call for RDP on/off request
Update to operate xenstore directly instead of a task

Signed-off-by: Hui Zhang <hui.zhang@citrix.com>