sys-fs/lvm2: improve dmeventd init

sys-fs/lvm2: improve dmeventd init

Upstream dmeventd has an exit-on-idle behavior that leads openrc to
decide that it has crashed, when it just exited "normally".

Provide multiple ways around this:
- supervisor support in the init script
- patch the daemon to make the idle timeout configurable (submitted upstream)

Co-authored-by: William Hubbs <williamh@gentoo.org>
Fixes: https://bugs.gentoo.org/682556
Package-Manager: Portage-2.3.62, Repoman-2.3.12
Signed-off-by: Robin H. Johnson <robbat2@gentoo.org>