install and use eventbroker from libdir

Signed-off-by: Sven Nierlein <sven@consol.de>
thruk-libs: pre/post depend on installation order

seems like its not predicable in which order rpms get installed or removed, even
with correct dependencies. So do some of the clean up things twice.

Signed-off-by: Sven Nierlein <sven@consol.de>