The problem is that the Table_locks_waited was incremented only
when the lock request succeed. If a thread waiting for the lock
gets killed or the lock request is aborted, the variable would
not be incremented, leading to inaccurate values in the variable.

The solution is to increment the Table_locks_waited whenever the
lock request is queued. This reflects better the intended behavior
of the variable -- show how many times a lock was waited.