Check old uploaded files when clicking Upload button

When user click "Choose Update File" button, it will call API: /check_before_upload
The new API "check_before_upload" will remove old .array files in webui_upload firectory and hold in config mode
After uploading completed, the config mode is released.
Add common function in utils for remove files in a given path of a directory
Because the upload function is a library, I only check it when the url path is in System Update page (/apv/system/management/update/_edit)