shimv2: fix the issue of stop container failed

There is no need to send another SIGKILL signal following
SIGTERM signal, otherwise, sending the SIGKILL signal would
get failed since the container process would has been terminated
by the previous SIGTERM signal.

Fixes:#1493

Signed-off-by: lifupan <lifupan@gmail.com>

containerd-shim-v2/service.go

@@ -634,19 +634,7 @@ func (s *service) Kill(ctx context.Context, r *taskAPI.KillRequest) (*ptypes.Emp
 		processID = execs.id
 	}
 
-	err = s.sandbox.SignalProcess(c.id, processID, signum, r.All)
-	if err != nil {
-		return nil, err
-	}
-
-	// Since the k8s will use the SIGTERM signal to stop a container by default, but
-	// some container processes would ignore this signal such as shell, thus it's better
-	// to resend another SIGKILL signal to make sure the container process terminated successfully.
-	if signum == syscall.SIGTERM {
-		err = s.sandbox.SignalProcess(c.id, processID, syscall.SIGKILL, r.All)
-	}
-
-	return empty, err
+	return empty, s.sandbox.SignalProcess(c.id, processID, signum, r.All)
 }
 
 // Pids returns all pids inside the container