Bugfix: Folder conflict dialog

* Fixed "Keep both" and "Skip" options in Firefox
* Fixed "Keep both" and "Skip" options when uploading via the "Upload"-menu
* Fixed broken "Upload"-menu after skipping all files (= no files uploaded)
* Fixed issues when uploading a folder into another folder which has or starts with the same name

https://github.com/owncloud/web/pull/7724
https://github.com/owncloud/web/issues/7680
