the `$parent` of `v-if` component isn't right

In the following example, the `if-child`'s `$parent` is the root Vue, not the `parent`. And the `repeat-child`'s `$parent` is properly the `parent`.

``` html
    <parent>
        <repeat-child v-repeat="repeat"></repeat-child>
        <if-child v-if="condition"></if-child>
    </parent>
```
