Remove unnecessary SCM checkout from Jenkinsfile

Change-Id: Iae80a5faeb0973a02564a8c8db9ae1a7b589d236

Jenkinsfile

diff --git a/Jenkinsfile b/Jenkinsfile
index ffe249c..94fae55 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -273,7 +273,6 @@
     stage('Preparing'){
         gerritReview labels: ['Verified': 0, 'Code-Style': 0]
 
-        checkout scm
         getChangeMetaData()
         collectBuildModes()
     }