CID 351372: Concurrent data access violations (ATOMICITY)

Triggered by 48b2a5df, c17eee03, and/or ae01ec28:

*** CID 351372:  Concurrent data access violations  (ATOMICITY)
/lib/isc/timer.c: 227 in timer_purge()
221     		LOCK(&timer->lock);
222     		if (!purged) {
223     			/*
224     			 * The event has already been executed, but not
225     			 * yet destroyed.
226     			 */
>>>     CID 351372:  Concurrent data access violations  (ATOMICITY)
>>>     Using an unreliable value of "event" inside the second locked section. If the data that "event" depends on was changed by another thread, this use might be incorrect.
227     			timerevent_unlink(timer, event);
228     		}
229     	}
230     }
231     
232     void