Fix branch name in Jenkinsfile

Change-Id: I910228d8de7285ffb2783cc1936bd5c8e8cac93f
diff --git a/Jenkinsfile b/Jenkinsfile
index a5cc3e5..3d36c04 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -11,7 +11,7 @@
         stage('Checkout') {
             steps {
                 cleanWs()
-                git branch: 'master',
+                git branch: '2018-09_respin',
                     url: 'git://git.eclipse.org/gitroot/simrel/org.eclipse.simrel.build'
             }
         }