Dockerfile: leave test-files in /code

Commit f385352 removed the content of
/code which is great for deployment images,
but breaks the integration tests.

Only remove .git* instead, since that is
the bulk of the size of the /code directory.

Dockerfile

@@ -43,7 +43,7 @@ WORKDIR $APPDIR
 # want to delete the stuff in the /code folder to keep it simple.
 RUN if [ "$ENVIRONMENT" = "deployment" ] ; then\
         pip install .[$ENVIRONMENT]; \
-        rm -rf /code/* /code/.??* ; \
+        rm -rf /code/* /code/.git* ; \
     else \
         pip install --editable .[$ENVIRONMENT]; \
     fi