fix attach-focus for dynamic change
fix attach-focus for dynamic change

This fixes an issue that the focus did not move when JS changed focusedIndex in the following example.

```
<li repeat.for="index of keywords">
  <input attach-focus.bind="focusedIndex === index">
```
aurelia/dialog,StrahilKazlachev/dialog,StrahilKazlachev/dialog,aurelia/dialog