Make apache2_mod_proxy work with Python 3, half-way modern Apache 2 versions, and add basic tests (#9762)
* Move Apache 2 installation to setup role.
* Make module work with Python 3.
* Add basic tests.
* Add changelog fragment.
* Simplify change.
* Pass referer.
(cherry picked from commit a3fd357d81)
Co-authored-by: Felix Fontein <felix@fontein.de>
patchback[bot]