We were ignoring the volume-type and volume-size parameters for
GCE; correct that.
Also add a release note. We forgot to do that. We may as well
attach it to the next version since it's a new feature, and only
with this change does it actually work as documented.
Change-Id: I6cad4fa7a661997771f9c7ccf622a5f9828bd750
5d37a0a6e1