syscalls/inotify: Extend tests to verify cookie value

Extend inotify01 and inotify02 tests to verify cookie value returned by
the kernel is sane (0 for all except rename events and matches for the
two rename events). There has been a kernel bug caused by commit
7053aee26a35 which would be caught by these tests.

Signed-off-by: Jan Kara <jack@suse.cz>