Allow the cleanup plugin to be disabled. Resolves #346 and others. May

need a more generic method to disable individual plugins later.

lib/units/device/plugins/cleanup.js

@@ -12,6 +12,10 @@ module.exports = syrup.serial()
     var log = logger.createLogger('device:plugins:cleanup')
     var plugin = Object.create(null)
 
+    if (!options.cleanup) {
+      return plugin
+    }
+
     function listPackages() {
       return adb.getPackages(options.serial)
     }