A "preview" space is created when saving a page

The firs report it's to found is this mail:
http://lists.xwiki.org/pipermail/users/2014-September/029114.html

I post this issue on Mon Dec 14 11:23:18 CET 2015 in the dev list:
http://lists.xwiki.org/pipermail/devs/2015-December/059800.html

For easy reproduce you can find my Docker-Container with Xwiki 7.3 and a docker-compose file on github:
https://github.com/OlafRadicke/xwiki/blob/master/docker-compose.yml

How ever I save a new version of a documented, I get a new
copy in preview, and the changes go never automatically to the target
place. After saving a document, the wiki jumps to the preview space
(with the new version). On the origin place, is still the firs version.

In the attachment you can see the result of this.