Update CI to JDK 16.

See #567.

Jenkinsfile

@@ -74,7 +74,7 @@ pipeline {
 					}
 				}
 
-				stage("test: baseline (jdk15)") {
+				stage("test: baseline (jdk16)") {
 					agent {
 						label 'data'
 					}
@@ -88,7 +88,7 @@ pipeline {
 					steps {
 						script {
 							docker.withRegistry('', 'hub.docker.com-springbuildmaster') {
-								docker.image('adoptopenjdk/openjdk15:latest').inside('-u root -v /var/run/docker.sock:/var/run/docker.sock -v /usr/bin/docker:/usr/bin/docker -v $HOME:/tmp/jenkins-home') {
+								docker.image('adoptopenjdk/openjdk16:latest').inside('-u root -v /var/run/docker.sock:/var/run/docker.sock -v /usr/bin/docker:/usr/bin/docker -v $HOME:/tmp/jenkins-home') {
 									sh "docker login --username ${DOCKER_HUB_USR} --password ${DOCKER_HUB_PSW}"
 									sh 'PROFILE=ci,java11 ci/test.sh'
 									sh "ci/clean.sh"