Step 1. Delete the update located in /cache/fota/ (may be /data/fota) and then click the update notification prompt to install it, it will instantly fail and the notification will disappear.
Step 2. Disable Otacerts.zip located in /etc/security by renaming it to otacerts.zip.bak
Step 3. Disable FotaClient.apk and FWUpgrade.apk by renaming with .bak extensions located in /system/app/
Step 4. Reboot
Sony Xperia Z2 tablet running 4.4.2 rooted with bootloader locked.