add install section to systemd service file

[dkriegner]

install section as used by Gentoo [1], Arch [2], and Fedora [3] was added to the systemd service file

[1] https://bugs.gentoo.org/show_bug.cgi?id=533380 [2] https://aur.archlinux.org/packages/tlsdate/ [3] https://bugzilla.redhat.com/show_bug.cgi?id=969723

[ghost]

This also fixed the issue on Raspbian. Why hasn't this been merged and the issue closed?

[zetok]

@jake-magee that's quite clear – upstream is dead.

Hopefully there is someone interested in taking over with maintenance.