fix Jenkinsfile Server stage

Jenkinsfile

@@ -85,9 +85,6 @@ pipeline {
 //            }
         }
         stage('Server') {
-         	when {
-                branch 'master'
-            }
             steps {
                 script {
                     FAILED_STAGE=env.STAGE_NAME
@@ -97,6 +94,7 @@ pipeline {
                         sh 'mvn --version'
                         sh "mvn -s $MAVEN_SETTINGS -pl -goofy-client clean install spring-boot:build-image -Dspring-boot.build-image.imageName=docker.ozg-sh.de/goofy:${IMAGE_TAG} -Dspring-boot.build-image.publish -Dmaven.wagon.http.retryHandler.count=3"
 
+ 						if (isMasterBranch()) {
 	                   		try {
 	    	                    dir('alfa-service'){
 	                                withSonarQubeEnv('sonarqube-ozg-sh'){
@@ -115,6 +113,7 @@ pipeline {
 	                    }
                     }
                 }
+            }
             post {
                 always{
                     junit testResults: '**/target/surefire-reports/*.xml', skipPublishingChecks: true