Use tini as init in all containers

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

docker/Dockerfile.gNB.ubuntu20

@@ -108,5 +108,6 @@ WORKDIR /opt/oai-gnb
 #EXPOSE 50000/udp # IF5 / ORI (control)
 #EXPOSE 50001/udp # IF5 / ECPRI (data)
 
-ENTRYPOINT ["/opt/oai-gnb/bin/entrypoint.sh"]
+COPY --from=gnb-base /tini /tini
+ENTRYPOINT ["/tini", "-v", "--", "/opt/oai-gnb/bin/entrypoint.sh"]
 CMD ["/opt/oai-gnb/bin/nr-softmodem", "-O", "/opt/oai-gnb/etc/gnb.conf"]