Revert "Stabilize the hostid for RPM installations."

Creating an /etc/hostid file as part of the rpm post install
causes problems for diskless systems which are sharing an image.
While it's still critical to ensure the hostid doesn't change
for zfs root filesystems. This will now be done by setting
the /etc/hostid in the initramfs created by dracut.

This reverts commit 79593b0dec57ee94c5bb56cdc2770ebde81ecea9.