Rehydration: Bound HTML attributes aren't rehydrated correctly

attn @rondale-sc

There seems to be an issue when rehydrating certain HTML attributes. I created a repro here: https://github.com/paulcwatts/rehydration-bug

I have a controller defined like this:
```
import Controller from '@ember/controller';
import { inject as service } from '@ember/service';

export default Controller.extend({
fastboot: service(),

buttonDisabled: true,
buttonEnabled: false
});
```

Within the template, I have a few buttons that are bound to various properties:

```
Disabled
Enabled
Disabled in Fastboot
```

You can see the expected and actual values here: https://github.com/paulcwatts/rehydration-bug/blob/master/app/templates/application.hbs

Two things that are interesting to note:

It appears to fail only if the attribute *changes* between when Fastboot renders and when the rehydration code operates. For instance in the second case (where it remains enabled), the rehydrated DOM is the same (the bare `disabled` attribute).

Secondly, I noticed it seems to work correctly if you insert some invalid HTML5 in the template. For instance, if you add: `` before the buttons, it works fine. Could it be the case where invalid HTML5 causes the rehydration code to bail out?