main/rng-tools: fix openrc service startup

fixes #12235
7 jobs for !16183 with issue-12235 in 1 minute and 25 seconds (queued for 1 second)
latest detached
Status Job ID Name Coverage
  Lint
passed #280018
docker-alpine x86_64
lint

00:00:18

 
  Build
passed #280023
docker-alpine ci-build aarch64
build-aarch64

00:00:49

passed #280024
docker-alpine ci-build armv7
build-armv7

00:00:50

passed #280022
docker-alpine ci-build ppc64le
build-ppc64le

00:01:03

passed #280021
docker-alpine ci-build s390x
build-s390x

00:00:42

passed #280020
docker-alpine ci-build x86
build-x86

00:00:32

passed #280019
docker-alpine ci-build x86_64
build-x86_64

00:00:38