ia32/futex: restore compat_robust_list

The same as for Checkpointing - we need to call 32-bit syscall
for compatible tasks here to correctly restore compat_robust_list,
not robust_list.

Note: I check here restorer's *task* arg for compatible mode, not
restorer *thread* arg. As changing application's mode during runtime
is very rare thing itself, application that runs different bitness
threads is most likely not present at all.
If we ever meet such application, this could be improved.

Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>