Pulling an image with option `stream=True` like this:
```
client.api.pull('docker.io/user/repo_name', tag='latest', stream=True)
```
without consuming the generator oftentimes results in premature drop of the connection. Docker daemon tries to send progress of pulling the image to the client, but it encounters an error (broken pipe) and therefore cancells the pull action:
```
Thread 1 "dockerd-dev" received signal SIGPIPE, Broken pipe.
ERRO[2018-09-03T05:12:35.746497638+02:00] Not continuing with pull after error: context canceled
```
As described in issue #2116, even though client receives response with status code 200, image is not pulled.

Closes #2116
Signed-off-by: Przemysław Adamek <adw1n@users.noreply.github.com>