You can use a file explorer like Root Explorer and rename /system/ etc/security/otacerts.zip to /system/ etc/security/otacerts.zip.bak AND freeze the system app com.smithmicro.dm with Titanium Backup. The otacerts.zip is what validates the new download is valid, so by renaming it, if it does download the OTA, it will not try to install because it cannot be verified. Just simply renaming this file can cause your battery life to tank, as it can cause the update to be repeatedly downloaded, so by freezing the download manager for the update, it cannot even try to download it. You want to do both, not just the download manager, as if it is already downloaded it could still try to install unless you change the otacerts.zip to otacerts.zip.bak.
Now if you want to later take the OTA, then just rename otacerts.zip.bak back to otacerts.zip and unfreeze the download manager and reboot and check for updates. Good luck and hope this helps!