Clean disk to install in pre

Installers frequently fail if there's a derelict lvm on disk.

Explicitly remove the on-disk content and deactive lvm to let
anaconda work reliably.

confluent_osdeploy/el8/profiles/default/scripts/pre.sh

@@ -93,5 +93,7 @@ if [ -e /tmp/installdisk -a ! -e /tmp/partitioning ]; then
     echo clearpart --all --initlabel >> /tmp/partitioning
     echo ignoredisk --only-use $(cat /tmp/installdisk) >> /tmp/partitioning
     echo autopart --nohome $LUKSPARTY >> /tmp/partitioning
+     dd if=/dev/zero of=/dev/$(cat /tmp/installdisk) bs=1M count=1
+     vgchange -a n
 fi
 kill $logshowpid