test: fix test datarace within driver shared eventer. (#19975)

drivers/shared/eventer/eventer_test.go

@@ -119,5 +119,8 @@ func TestEventer_iterateConsumers(t *testing.T) {
 	ev1, ok := <-consumer
 	require.False(ok)
 	require.Nil(ev1)
+
+	e.consumersLock.RLock()
 	require.Equal(0, len(e.consumers))
+	e.consumersLock.RUnlock()
 }