Use tini as init in all containers

- Print problems, e.g., segfault
- Handle signals and zombie processes properly

docker/Dockerfile.base.ubuntu20

@@ -46,6 +46,12 @@ RUN apt-get update && \
        python3-pip && \
     pip3 install --ignore-installed pyyaml
 
+# Add "Tini - A tiny but valid init for containers", https://github.com/krallin/tini
+# it will be copied into target containers, to print exit numbers and handle signals properly
+ENV TINI_VERSION v0.19.0
+ADD https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini /tini
+RUN chmod +x /tini
+
 # In some network environments, GIT proxy is required
 RUN /bin/bash -c "if [[ -v NEEDED_GIT_PROXY ]]; then git config --global http.proxy $NEEDED_GIT_PROXY; fi"