ODROID: change default user and groups

This patch is to change default user and groups to 'odroid' instead of
'linaro'.

Signed-off-by: Dongjin Kim <tobetter@gmail.com>
ODROID: change hostname

The hostname is changed to 'odroid-ubuntu-desktop'.

Signed-off-by: Dongjin Kim <tobetter@gmail.com>
ODROID: change default login account

Signed-off-by: Dongjin Kim <tobetter@gmail.com>