Notify systemd also for readonly instances

Otherwise they won't be able to start.
4 jobs for master in 1 minute and 34 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build Pkgsrc
passed #11127
build_pkgsrc:stretch

00:00:17

 
  Build Pkg
passed #11128
amd64
build_pkg:stretch:amd64

00:00:59

passed #11129
arm64
build_pkg:stretch:arm64

00:00:40

 
  Upload Pkg
passed #11130
upload_pkg

00:00:17