Use domainname as ejabberd host.
Only use hostname when domainname is blank. This fixes the 1st and 2nd TODOs from https://github.com/freedombox/Plinth/issues/83. This change adds a dependency on python3-yaml.
Only use hostname when domainname is blank. This fixes the 1st and 2nd TODOs from https://github.com/freedombox/Plinth/issues/83. This change adds a dependency on python3-yaml.