ENH: Upgraded Debian and JDK for CI pipeline.

src/test/docker/Dockerfile

-FROM debian:stretch
+FROM debian:buster
 RUN apt-get update && \
-	apt-get install git make mariadb-server maven openjdk-8-jdk-headless \
+  apt-get install \
+      git make mariadb-server maven openjdk-11-jdk-headless \
       python3-pip screen libpam0g-dev unzip curl shunit2 -y