staging/lustre: Remove unused lu_object functions.

Quite a bunch of them are only used on the server.
lu_object_put_nocache, lu_object_invariant, lu_dev_del_linkage,
lu_context_tags_update, lu_context_tags_clear, lu_session_tags_update,
lu_session_tags_clear, lu_env_refill_by_tags, lu_printk_printer,
lu_object_assign_fid, lu_object_anon, lu_buf_free, lu_buf_alloc,
lu_buf_realloc, lu_buf_check_and_alloc, lu_buf_check_and_grow

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>