Coverity missing lock warning 9.11

*** CID 306682:  Concurrent data access violations  (MISSING_LOCK)
/lib/isc/tests/task_test.c: 799 in manytasks()
793     	result = isc_mem_create(0, 0, &mctx);
794     	assert_int_equal(result, ISC_R_SUCCESS);
795     
796     	result = isc_taskmgr_create(mctx, 4, 0, &taskmgr);
797     	assert_int_equal(result, ISC_R_SUCCESS);
798     
   CID 306682:  Concurrent data access violations  (MISSING_LOCK)
   Accessing "done" without holding lock "lock". Elsewhere, "done" is accessed with "lock" held 8 out of 9 times.
799     	done = false;
800     
801     	event = isc_event_allocate(mctx, (void *)1, 1, maxtask_cb,
802     				   (void *)ntasks, sizeof(*event));
803     	assert_non_null(event);
804