packaging: spec: clean old index files

ovirt-engine<=3.2 created files at /usr, among other are the jboss index
files.

these files must be removed or application will not start after upgrade,
as jboss makes assumptions.

Change-Id: Ifdd78cc9884035992a43eca3a7d5ca27d63a2b18
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>