Removed "postun"install block since it fails and prevents upgrades/removes.

Got these during upgrades/removes:

```
error: %postun(storm-drpc-0.9.0_wip16-4.noarch) scriptlet failed, exit status 2
Non-fatal POSTUN scriptlet failure in rpm package 
```

which can also lead to duplicate packages being installed during upgrade.

This doesn't seem to be necessary since there is a %preun - and the reason it's failing is that at post-un stage /etc/init.d/storm-%1 no longer exists.