restore: clear breakpoints only for alive tasks

We don't set breakpoints for zombies.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
check: make check_ptrace_peeksiginfo and check_sigqueuinfo as static

They are not used outside.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>