Bug fix: stats --no-stream always print zero values

`docker stats --no-stream` always print zero values.

```
$ docker stats --no-stream
CONTAINER           CPU %               MEM USAGE / LIMIT   MEM %
NET I/O             BLOCK I/O
7f4ef234ca8c        0.00%               0 B / 0 B           0.00%
0 B / 0 B           0 B / 0 B
f05bd18819aa        0.00%               0 B / 0 B           0.00%
0 B / 0 B           0 B / 0 B

```

This commit will let docker client wait until it gets correct stat
data before print it on screen.

Signed-off-by: Zhang Wei <zhangwei555@huawei.com>