MAR-114: Moved set_fact for wsgi_website and php_website roles:

- Moved set_fact for setting application admin, user, and home directory into
defaults/main.yml.
- Updated test playbook for wsgi_website to fixate the ptpython and dnspython
versions (including their dependencies).
- Updated tests for wsgi_website to use new fixated versions for ptpython,
dnspython, and their dependencies.