adb shell spwns non-root shell for -tests builds

Hey

So this issue has kept me up all night today.

It seems that 'adb shell' gives me a non-root 'shell' account when using -tests build that uses TARGET_BUILD_VARIANT=tests. I've patched this and rebuilt but without success.

My patch and rationale is here: [1], any ideas about why it is not working, what might be missing, etc - are welcome.

For context, adb shell needs to give me a root account for lava-android-test to work properly.

Thanks ZK

[1]: http://review.android.git.linaro.org/#change,2671