Rollback to deprecated "logrotate" JJB option

sre-ci dislikes new parameter

Change-Id: I124e1b125343b02f167f9ea6b768e6b5f9492847
diff --git a/jobs/templates/download-config-drive.yml b/jobs/templates/download-config-drive.yml
index 94269ec..d636dbc 100644
--- a/jobs/templates/download-config-drive.yml
+++ b/jobs/templates/download-config-drive.yml
@@ -105,9 +105,9 @@
 
       }}
     name: download-config-drive
-    build-discarder:
-      days-to-keep: 365
-      artifact-days-to-keep: 60
+    logrotate:
+      DaysToKeep: 365
+      artifactDaysToKeep: 60
     parameters:
     - string:
         default: ''