while accessing table->locks or un_member.tab_lock.locks.
This is related to Issue #158.  According to static analysis,
the added debug assertions should always hold.

lock_table_has_to_wait_in_queue(), lock_queue_iterator_reset(),
lock_queue_iterator_get_prev(), add_trx_relevant_locks_to_cache(),
fetch_data_into_cache(): Add ut_ad(mutex_own(&kernel_mutex)).