net-mgmt/icingaweb2-module-director: Enable Icinga Director Background Daemon

Deploys in the director don't work/finish since the last update. The
reason is, that the update didn't enable the Icinga Director Background
Daemon, that has been mandatory since 1.7.0, see
https://github.com/Icinga/icingaweb2-module-director/blob/master/doc/75-Background-Daemon.md

PR: 269227
Reported by: flo
Sponsored by: Netzkommune GmbH