Bumped docker-py version to latest release

Signed-off-by: Joffrey F <joffrey@docker.com>

Dockerfile

@@ -117,7 +117,7 @@ RUN git clone -b buildroot-2014.02 https://github.com/jpetazzo/docker-busybox.gi
 RUN curl -sSL -o /cirros.tar.gz https://github.com/ewindisch/docker-cirros/raw/1cded459668e8b9dbf4ef976c94c05add9bbd8e9/cirros-0.3.0-x86_64-lxc.tar.gz
 
 # Get the "docker-py" source so we can run their integration tests
-RUN git clone -b 0.7.0 https://github.com/docker/docker-py.git /docker-py
+RUN git clone -b 0.7.1 https://github.com/docker/docker-py.git /docker-py
 
 # Setup s3cmd config
 RUN { \