logrotate: use new etc.install overwrite handling.
peervpn: use new etc.install overwrite handling.
redis: use new etc.install overwrite handling.
redis: remove 2.4 upgrade path, no longer needed.
lighttpd: remove unneeded post_install.
mariadb: move var mkpath to install.
mongodb: move some post_install back to install.
mysql: move some post_install back to install.