Android : Android L Preview: Attempting Task Locking By Rooting

I am attempting to test whether task locking in Android L Preview can be accomplished by rooting the device rather than building a custom ROM.

I've created a 'device_owner.xml' file and placed in \data\system.

<?xml version='1.0' encoding='utf-8'?>
<device-owner>
    package="com.ta.instrumentcontroller"
    name="TA Instrument Controller"
</device-owner>

Upon reboot, the Nexus 7 2013 tablet just sits at the 'Bouncing Android Balls' logo. If I go into TWRP and delete the file, the boot sequence completes.

Does anyone know what might be going on?