Fix docker restart panic on machine ungracefully shutdown
Machine ungracefully shutdown leaves a lot of container has a
Running=true state.
```
$ cat config.v2.json | jq .
"Running": true,
"Paused": false,
"Restarting": false,
```
And the next docker start will fail with panic.
```
time="2016-12-01T01:54:45.086446715-05:00" level=warning msg="libcontainerd: client is out of sync, restore was called on a fully synced container (49f41ad5ca0be860622d9190673b5816d012022fb2c1794560ec4851e7cfec6a)."
time="2016-12-01T01:54:45.087046004-05:00" level=warning msg="libcontainerd: failed to retrieve container 49f41ad5ca0be860622d9190673b5816d012022fb2c1794560ec4851e7cfec6a state: rpc error: code = 2 desc = containerd: container not found"
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x8 pc=0x5db7f3]
goroutine 57 [running]:
panic(0x16a8e60, 0xc420010130)
/usr/local/go/src/runtime/panic.go:500 +0x1a1
github.com/docker/docker/libcontainerd.(*client).Restore(0xc4202e1a40, 0xc420415000, 0x40, 0xc42015a0b0, 0x0, 0x0, 0x0, 0x0, 0x0)
/go/src/github.com/docker/docker/libcontainerd/client_linux.go:457 +0x553
github.com/docker/docker/daemon.(*Daemon).restore.func1(0xc4201c46f0, 0xc4202581e0, 0xc4201c46e8, 0xc42047bfb0, 0xc42047bf80, 0xc42047bf50, 0xc42024ba10, 0xc420512c00)
/go/src/github.com/docker/docker/daemon/daemon.go:205 +0x198
created by github.com/docker/docker/daemon.(*Daemon).restore
/go/src/github.com/docker/docker/daemon/daemon.go:260 +0x7bb
```
Signed-off-by: Lei Jitang <leijitang@huawei.com>
267422e4d0