build maven and image as separate step in order to avoid double maven-source-plugin calls

Jenkinsfile

@@ -163,7 +163,8 @@ pipeline {
 
                     configFileProvider([configFile(fileId: 'maven-settings', variable: 'MAVEN_SETTINGS')]) {
                         sh 'mvn --version'
-                        sh "mvn --no-transfer-progress -s $MAVEN_SETTINGS -pl -alfa-client clean install spring-boot:build-image -Dspring-boot.build-image.imageName=docker.ozg-sh.de/alfa:${IMAGE_TAG} -Dspring-boot.build-image.publish -Dmaven.wagon.http.retryHandler.count=3"
+                        sh "mvn -s $MAVEN_SETTINGS -pl -alfa-client clean install"
+                        sh "mvn --no-transfer-progress -s $MAVEN_SETTINGS -pl -alfa-client spring-boot:build-image -Dspring-boot.build-image.imageName=docker.ozg-sh.de/alfa:${IMAGE_TAG} -Dspring-boot.build-image.publish -Dmaven.wagon.http.retryHandler.count=3\""
 
  						if (isMasterBranch()) {
 	                   		try {