Changed SignalProcess to use new hcsshim API

Signed-off-by: Darren Stahl <darst@microsoft.com>

libcontainerd/client_windows.go

@@ -324,7 +324,7 @@ func (clnt *client) SignalProcess(containerID string, processFriendlyName string
 
 	for _, p := range cont.processes {
 		if p.friendlyName == processFriendlyName {
-			return hcsshim.TerminateProcessInComputeSystem(containerID, p.systemPid)
+			return p.hcsProcess.Kill()
 		}
 	}