Confirmed by testing the behavior of various varnish versions.

If a VCL was reloaded at the date of this commit, it would change from:

    reload_20170321T174643

to

    reload_20170321_174643

This gives second resolution to the reload's name but keeps the name
compact, parseable, and naturally sorted. An example is displayed with
the usage error message.

It was there to test a failure...

* varnish autostarts and is enabled
* varnishncsa does not start and is disabled
need to do ``systemctl enable varnishncsa`` to enable it

We want the behaviour on systemd and non systemd installs to be
identical. Varnishd should be enabled and started automatically
but varnishncsa requires manual enabling.

When BINDISTS include a legacy (non-systemd) distro, we will use
the old versions of ``debian/control`` and ``debian/rules``, for
any other distro we will use the systemd enabled files.

Bring back the dh-systemd files and keep a non-systemd version
separate in ``debian/control.nosystemd`` and ``debian/rules.nosystemd``