fedora-common: Clear out machine-id

Apparently something is populating `/etc/machine-id` at install time
now, which prevents units scheduled to run on first boot (with
`ConditionFirstBoot=true`) from starting.

fedora-common.ks

@@ -46,6 +46,8 @@ services --enabled systemd-networkd,systemd-resolved,ssh-host-certs-renew.timer,
 %post --erroronfail
 export NO_PROXY='pyrocufflink.blue,*.pyrocufflink.blue'
 
+echo uninitialized > /etc/machine-id
+
 echo 'install_weak_deps=0' >> /etc/dnf/dnf.conf
 echo 'deltarpm=0' >> /etc/dnf/dnf.conf
 echo '%_excludedocs 1' >> /etc/rpm/macros