CRIU processes save *.gcda and *.gcno files near source files,
so when we restore tests into another mount namespace,
we need to have access to sources from this namespace.

Cc: Sergey Bronnikov <sergeyb@openvz.org>
Reported-by: Sergey Bronnikov <sergeyb@openvz.org>
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>