parasite: wait for any child process

If parasite exited unexpectedly, CRIU gets SIGCHLD and handles it.
In sigchld handler we need to wait any child process.
Currently criu waits neighbours in its group, but a dumped
processes is in another group usually. Here is a typo.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

parasite-syscall.c

@@ -346,7 +346,7 @@ static void sigchld_handler(int signal, siginfo_t *siginfo, void *data)
 	pr_err("si_code=%d si_pid=%d si_status=%d\n",
 		siginfo->si_code, siginfo->si_pid, siginfo->si_status);
 
-	pid = waitpid(0, &status, WNOHANG);
+	pid = waitpid(-1, &status, WNOHANG);
 	if (pid <= 0)
 		return;