mm, right, the microcode_ctl DB entry only exists on SME8, not SME9 (for which there's no init script, so the db entry won't do anything). ON EL6 and above, microcode_ctl is handled by udev (see /lib/udev/rules.d/89-microcode.rules). You can probably disable it with something like (not tested)
echo "install microcode /bin/true" > /etc/modprobe.d/microcode
signal-event reboot