Fix critical bug: can't restart a restarting container

When user try to restart a restarting container, docker client report
error: "container is already active", and container will be stopped
instead be restarted which is seriously wrong.

What's more critical is that when user try to start this container
again, it will always fail.

This error can also be reproduced with a `docker stop`+`docker start`.

And this commit will fix the bug.

Signed-off-by: Zhang Wei <zhangwei555@huawei.com>
Upstream-commit: a705e166cf3bcca62543150c2b3f9bfeae45ecfa
Component: engine

components/engine/libcontainerd/client_linux.go

@@ -134,7 +134,7 @@ func (clnt *client) Create(containerID string, spec Spec, options ...CreateOptio
 	defer clnt.unlock(containerID)
 
 	if ctr, err := clnt.getContainer(containerID); err == nil {
-		if ctr.restarting { // docker doesn't actually call start if restart is on atm, but probably should in the future
+		if ctr.restarting {
 			ctr.restartManager.Cancel()
 			ctr.clean()
 		} else {