GCE networks are created in "Legacy" mode

GCE reports:
<img width="351" alt="screen shot 2016-12-23 at 2 24 51 am" src="https://cloud.githubusercontent.com/assets/882455/21449109/d38d361e-c8b7-11e6-8168-d2af93c80396.png">

I'm guessing this is related to #519.