e_dnd: Send mouse down/up event to KVM service when drag cancelled by KVM

e_dnd: Send mouse down/up event to KVM service when drag cancelled by KVM

The basic DnD operation involves E20 sending a mouse up event to client
once dragging begins on the client, followed by the actual DnD operation.

This patch adresses the issue where the KVM service needs to be informed
when is mouse is released, even after the KVM itself cancels the drag.

< Scenario >
1. Draggging starts on the Browser.
2. The KVM service app requests cancel drag.
3. When the mouse button is released, KVM service has no way to detect it
since no mouse up event is sent to.

Change-Id: I8501e12294129211ff941742703fe29edaa975b8