Most likely still there
This thing was no accident. One of the research papers linked to from that SE post shows Coolpad is the source of the backdoor and that they were still actively developing it in 2014.
https://www.scmagazineuk.com/hidden-backdoor-in-up-to-10m-android-phones/article/540936/
This one adds that you can uninstall CoolReaper with root privileges, so root and a vanilla ROM image should prevent it from returning via an OTA update.
https://www.scmagazineuk.com/hidden-backdoor-in-up-to-10m-android-phones/article/540936/
This one adds that you can uninstall CoolReaper with root privileges, so root and a vanilla ROM image should prevent it from returning via an OTA update.