Use Java 8 to build snapshots for Artifactory.

Closes #3976

Author: mp911de

Jenkinsfile

@@ -233,7 +233,7 @@ pipeline {
 			steps {
 				script {
 					docker.withRegistry(p['docker.registry'], p['docker.credentials']) {
-						docker.image(p['docker.java.lts.image']).inside(p['docker.java.inside.basic']) {
+						docker.image(p['docker.java.main.image']).inside(p['docker.java.inside.basic']) {
 							sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -v'
 							sh 'MAVEN_OPTS="-Duser.name=jenkins -Duser.home=/tmp/jenkins-home" ./mvnw -s settings.xml -Pci,artifactory ' +
 									'-Dartifactory.server=https://repo.spring.io ' +