Add minio & rclone to our functional tests

It is now possible to configure which clients
you do not want to test with the env variable SKIP_XXX=1,
XXX being the client name. eg. SKIP_S3CMD=1 ./script/test-smoke.sh

script/builder_image/Dockerfile

@@ -1,6 +1,7 @@
 FROM rust:buster
 RUN apt-get update && \
-	apt-get install --yes libsodium-dev awscli python-pip && \
+	apt-get install --yes libsodium-dev awscli python-pip wget rclone openssl socat && \
 	    rm -rf /var/lib/apt/lists/*
+RUN wget https://dl.min.io/client/mc/release/linux-amd64/mc -O /usr/local/bin/mc && chmod +x /usr/local/bin/mc
 RUN rustup component add rustfmt
 RUN pip install s3cmd