Fix dockerfile agent checkout ordering

Jenkinsfile

@@ -7,7 +7,6 @@ pipeline {
   }
 
   options {
-    skipDefaultCheckout()
     timestamps()
     disableConcurrentBuilds()
   }
@@ -53,7 +52,11 @@ pipeline {
 
   post {
     always {
-      cleanWs deleteDirs: true, disableDeferredWipeout: true
+      script {
+        if (getContext(hudson.FilePath)) {
+          cleanWs deleteDirs: true, disableDeferredWipeout: true
+        }
+      }
     }
   }
 }