Set ro.fw.mu.headless_system_user with PRODUCT_SYSTEM_DEFAULT_PROPERTIES

bug: 126582117
Test: lunch gcar_emu_x86-userdebug && m && emulator.
lunch hawk-userdebug && m; deploy

boot... am get-current-user is 10

Change-Id: I9973c85a80029cba0ea8b8790fcdb015c3fb8618
1 file changed