1091427: pulp-server should run systemctl daemon-reload on upgrade/removal

Some systemd macros were missing from the pulp-server spec to automatically run
systemctl daemon-reload. Adding to %postun covers both upgrades and removals.

This could be done in %post as well, but doing it only in %postun seems to be the
convention. A macro [exists](http://cgit.freedesktop.org/systemd/systemd/tree/src/core/macros.systemd.in) for %postun but not for %post. 

To test, you will have to update the rpm *twice*. The first update will put the script in %postun, but it will not actually get executed until the second update. Verification can be done via `journalctl | tail`, output will look like this on success:

```
May 02 13:33:30 localhost.localdomain systemd[1]: Reloading.
<other mesages related to reloading>
```