Group doesn't initialize blendMode properly due to race condition with UIComponent's $blendMode

Steps to reproduce:
1. Run the attached app.
2. Click the third button to disable the second button.

Actual Results:
The second button looks different from the first. (different blendModes)

Expected Results:
The first button should initialize correctly.

Workaround (if any):
none

The issue lies in commitProperties of Group. We initialize blendMode there as "normal" and call super.commitProperties after. However, in super.commitProperties, we set the component's alpha to 0.5, which, in turn, tries to change the blendMode to "layer". But because we are already in commitProperties, the blendMode change doesn't resolve leaving us with the initial blendMode and an ugly button.