testing: re-add cinnabar cloning to test-runner* image build (Bug 1…

…748903)

We removed this since we don't need to build the cinnabar helper
for testing any more, but we still need the `cinnabarclone.py` file
from the repo for some tests.

testing/docker/test-runner-py2/Dockerfile

@@ -61,6 +61,11 @@ RUN chown -R vct:vct /app
 
 USER vct
 
+# clone cinnabar for the `cinnabarclone` extension
+RUN git clone \
+    --branch release \
+    https://github.com/glandium/git-cinnabar.git $VIRTUAL_ENV/git-cinnabar
+
 WORKDIR /app
 
 # Install editable requirements py2/py3

testing/docker/test-runner/Dockerfile

@@ -79,6 +79,10 @@ RUN pip install -e vct/pylib/vcsreplicator
 RUN pip install -e vct/hghooks
 RUN pip install -e vct/testing
 
+# clone cinnabar for the `cinnabarclone` extension
+RUN git clone \
+    --branch release \
+    https://github.com/glandium/git-cinnabar.git /app/venv/git-cinnabar
 WORKDIR /app/vct
 
 # Install Mercurials