title: Bug: Varnish 4 install on CentOS 7 (systemctl)
body: <p>Installed Varnish from yum; but immediate error when initiating via systemctl. </p>
  
  <pre><code>Jul 28 14:11:54 localhost.localdomain varnishd[6546]: .init_func = VGC_function_vcl_init,
  Jul 28 14:11:54 localhost.localdomain varnishd[6546]: .fini_func = VGC_function_vcl_fini,
  Jul 28 14:11:54 localhost.localdomain varnishd[6546]: };
  Jul 28 14:11:54 localhost.localdomain varnishd[6557]: Assert error in main(), mgt/mgt_main.c line 686:
  Jul 28 14:11:54 localhost.localdomain varnishd[6557]: Condition((daemon(1,0)) == 0) not true.
  Jul 28 14:11:54 localhost.localdomain varnishd[6557]: errno = 19 (No such device)
  Jul 28 14:11:54 localhost.localdomain systemd[1]: Failed to read PID from file /var/run/varnish.pid: Invalid argument
  Jul 28 14:11:54 localhost.localdomain systemd[1]: varnish.service never wrote its PID file. Failing.
  Jul 28 14:11:54 localhost.localdomain systemd[1]: Failed to start Varnish a high-perfomance HTTP accelerator.
  Jul 28 14:11:54 localhost.localdomain systemd[1]: Unit varnish.service entered failed state.
  </code></pre>
  
  <p>SELinux is disabled; package was installed via root.  This is a fresh install.</p>