Fix __project_dir initialisation and change kdist__get_topdir() and Co behaviours

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
Use kdist__restricted_mode() instead of testing KDIST__RESTRICTED_MODE value

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
show the calltrace in bug()

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>