As we remove the default ``-S``, we no longer care about
handling the ``/etc/varnish/secret`` file.

Discussion in #84

Suggested in #87 to ensure that the network is fully initialised.

Unify the varnishncsa.service between the two.

This will make the service work out of the box by a simple
``systemctl enable varnishncsa``, as using the pidfile requires
``/var/run/varnishncsa`` to be created.

This is in line with the ``varnish.service`` anyway.

Due to https://github.com/varnishcache/varnish-cache/issues/2316
we cannot reliably config-test the VCL in the init-script.
If users want to configtest the VCL in advance of a restart, this
can be done with loading the new VCL into the running varnish, or
running ``varnishd -C`` with a different option-set that will not
conflict with the running instance(s).

And make it possible to reload several labels in a short time. Make sure
the date is always UTC.

Revert back to the old dirty read trick.

According to the manual it should be possible to use the {n} notation in
regular expressions but for some reason it doesn't work here.

This reverts commit b8a0ea97.

I'm not convinced that we want to prevent reloaded VCLs to cool down
after subsequent reloads.

Otherwise the warmup delay might be ineffective.