This change adds an independent class for [retry_scheduler] parameters,
because these parameters are used not by the api service but the retry
daemon.
Currently no distro provides a package to install the service so
the new class only set parameters, which is incomplete. This will be
fixed once the packaging issue is resolved.
Change-Id: Ib8b649c2e5ac5fee5e5a3bd52caeb21780fc1f61