Make code self-documenting

tools/jenkins/build_docker_and_run_tests.sh

@@ -63,7 +63,7 @@ docker run \
   -e "arch=$arch" \
   -e CCACHE_DIR=/tmp/ccache \
   -e XDG_CACHE_HOME=/tmp/xdg-cache-home \
-  -e THIS_IS_REALLY_NEEDED='                           ' \
+  -e THIS_IS_REALLY_NEEDED='see https://github.com/docker/docker/issues/14203 for why docker is awful' \
   -i $TTY_FLAG \
   -v "$git_root:/var/local/jenkins/grpc" \
   -v /tmp/ccache:/tmp/ccache \