Fix test-docker-py on some arches

When running 'make all' on armhf, I got this:

> ---> Making bundle: .integration-daemon-start (in bundles/17.06.0-dev/test-docker-py)
> Using test binary docker
> INFO: Waiting for daemon to start...
> Starting dockerd
> .
> Traceback (most recent call last):
>   File "/usr/local/lib/python2.7/dist-packages/_pytest/config.py", line
> 320, in _importconftest
>     mod = conftestpath.pyimport()
>   File "/usr/local/lib/python2.7/dist-packages/py/_path/local.py", line
> 662, in pyimport
>     __import__(modname)
>   File "/docker-py/tests/integration/conftest.py", line 6, in <module>
>     import docker.errors
>   File "/docker-py/docker/__init__.py", line 2, in <module>
>     from .api import APIClient
>   File "/docker-py/docker/api/__init__.py", line 2, in <module>
>     from .client import APIClient
>   File "/docker-py/docker/api/client.py", line 11, in <module>
>     from .build import BuildApiMixin
>   File "/docker-py/docker/api/build.py", line 6, in <module>
>     from .. import auth
>   File "/docker-py/docker/auth.py", line 6, in <module>
>     import dockerpycreds
> ImportError: No module named dockerpycreds
> ERROR: could not load /docker-py/tests/integration/conftest.py

The fix for this was already provided by commit 0ec8f56a3 and
commit c7c923594, but for some reason it did not made its way
to Dockerfiles for all architectures.

While at it, remove excessive comments.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

Dockerfile

@@ -149,9 +149,6 @@ RUN set -x \
 # Get the "docker-py" source so we can run their integration tests
 ENV DOCKER_PY_COMMIT a962578e515185cf06506050b2200c0b81aa84ef
 # To run integration tests docker-pycreds is required.
-# Before running the integration tests conftest.py is
-# loaded which results in loads auth.py that
-# imports the docker-pycreds module.
 RUN git clone https://github.com/docker/docker-py.git /docker-py \
 	&& cd /docker-py \
 	&& git checkout -q $DOCKER_PY_COMMIT \

Dockerfile.aarch64

@@ -125,9 +125,7 @@ RUN set -x \
 
 # Get the "docker-py" source so we can run their integration tests
 ENV DOCKER_PY_COMMIT a962578e515185cf06506050b2200c0b81aa84ef
-# Before running the integration tests conftest.py is
+# To run integration tests docker-pycreds is required.
-# loaded which results in loads auth.py that
-# imports the docker-pycreds module.
 RUN git clone https://github.com/docker/docker-py.git /docker-py \
 	&& cd /docker-py \
 	&& git checkout -q $DOCKER_PY_COMMIT \

Dockerfile.armhf

@@ -118,9 +118,11 @@ RUN set -x \
 
 # Get the "docker-py" source so we can run their integration tests
 ENV DOCKER_PY_COMMIT a962578e515185cf06506050b2200c0b81aa84ef
+# To run integration tests docker-pycreds is required.
 RUN git clone https://github.com/docker/docker-py.git /docker-py \
 	&& cd /docker-py \
 	&& git checkout -q $DOCKER_PY_COMMIT \
+	&& pip install docker-pycreds==0.2.1 \
 	&& pip install -r test-requirements.txt
 
 # Set user.email so crosbymichael's in-container merge commits go smoothly

Dockerfile.ppc64le

@@ -117,9 +117,11 @@ RUN set -x \
 
 # Get the "docker-py" source so we can run their integration tests
 ENV DOCKER_PY_COMMIT a962578e515185cf06506050b2200c0b81aa84ef
+# To run integration tests docker-pycreds is required.
 RUN git clone https://github.com/docker/docker-py.git /docker-py \
 	&& cd /docker-py \
 	&& git checkout -q $DOCKER_PY_COMMIT \
+	&& pip install docker-pycreds==0.2.1 \
 	&& pip install -r test-requirements.txt
 
 # Set user.email so crosbymichael's in-container merge commits go smoothly

Dockerfile.s390x

@@ -110,9 +110,11 @@ RUN set -x \
 
 # Get the "docker-py" source so we can run their integration tests
 ENV DOCKER_PY_COMMIT a962578e515185cf06506050b2200c0b81aa84ef
+# To run integration tests docker-pycreds is required.
 RUN git clone https://github.com/docker/docker-py.git /docker-py \
 	&& cd /docker-py \
 	&& git checkout -q $DOCKER_PY_COMMIT \
+	&& pip install docker-pycreds==0.2.1 \
 	&& pip install -r test-requirements.txt
 
 # Set user.email so crosbymichael's in-container merge commits go smoothly