Another option is to just "disable' the fota packages - this way you could always re-enable them if needed later.|
From shell prompt, "pm list packages|grep -i fota" (this will list all OTA-related packages)
To disable them, "pm disable com.adups.fota" and "pm disable com.adups.fota.sysoper".
If need be, you can always re-enable them with "pm enable ...".
Like I said, just another possible alternative.