Support enrolling into Demo Mode on a Chrome OS for Linux build.

Currently, enrollment with the DM server fails:

[104527:104527:1112/143130.809128:ERROR:demo_setup_controller.cc(755)] DemoSetupError (code: 5, recovery: 5) : EnrollmentError: (status: 2, client_status: 1, store_status: 0, validation_status: 0, lock_status: 0)