kvm tool: Exit init only when /bin/sh itself stops

Right now we wait for any of the children to stop, which means we might
exit before /bin/sh stopped.

Instead, wait only for the /bin/sh (or the sandboxed) process.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

guest/init_stage2.c

@@ -48,7 +48,7 @@ int main(int argc, char *argv[])
 		else
 			run_process("/bin/sh");
 	} else {
-		wait(&status);
+		waitpid(child, &status, 0);
 	}
 
 	reboot(LINUX_REBOOT_CMD_RESTART);