Fix Backend

Align the wrapper script to have the correct behavior
Remove setuid bit in package-helper
Adapt the user check function for xwalkctl binary

BUG=XWALK-1731

Signed-off-by: Baptiste DURAND <baptiste.durand@open.eurogiciel.org>
Signed-off-by: Sabera Djelti (sdi2) <sabera.djelti@open.eurogiciel.org>