Redmine#5556: def.cf defaults should be $(sys.domain) instead of "example.com"

(cherry picked from commit c3387c29e23aa923628ebb94fa740f07ad189250)
Redmine#5556: mix def.acl and def.domain at the source

(cherry picked from commit 38cee84faa28c5bbba6af39e4d0740c11fdf8a37)