[TIZEN] Check User ID and return immediatly if Root attempts to execute x...

[TIZEN] Check User ID and return immediatly if Root attempt to execute xwalkctl

Root user is not allowed to manage application. This has non sense on Tizen.

So calling xwalkctl as root should return also an error.

BUG=XWALK-2749
Signed-off-by: Baptiste DURAND <baptiste.durand@open.eurogiciel.org>
Question: Does "xwalk_tizen_check_user_for_xwalkctl()" report error? If not, I'd suggest you need report here before exit.