How do I get the standard default.prop file back on the root file system?

Question

At the root file system on my Android phone, there's a file called default.prop. Right now that's a non-standard file because of CF Auto Root, but I want that file to be the stock version (1).

After what I have understood, /default.prop file is overwritten on every boot from a default.prop file within the boot partition.

My phone is rooted with CF-Auto-Root, but I've replaced the boot and bootloader partitions with factory image versions:

$ fastboot flash bootloader bootloader.img
$ fastboot flash boot boot.img

But still I get the non-stock default.prop file. What am I doing wrong?

 

(1) This is because I'm trying to upgrade to Android 5.1, and right now I'm getting an error because "this device has google/omni_hammerhead/hammerhead:4.4.4/KTU84P/eng.dees_troy.20150214.172938:eng/test-keys".

Answer 1

I'll just quote Elluel on XDA:

Don't bother messing with reverting everything just to update, it is extremely unlikely to work since as of Lollipop Google has changed the OTA method to check the sum of the entire partition rather than only what it cares about.

Download the 5.1 factory images, and flash system.img, boot.img, cache.img, radio.img and bootloader.img (don't flash userdata.img unless you want to wipe all your data), then boot into a custom recovery and flash the latest SuperSU (http://download.chainfire.eu/supersu).

It doesn't answer the question here directly, but it ultimately solved what I was trying to achieve.