Add the LAUNCH_INSTANCE_DEFAULTS.default_availability_zone settings in
VM creation dashboard in order to let administrator select a default
availability zone instead of a random one when many are available.
Co-Authored-By: Akihiro Motoki <amotoki@gmail.com>
Change-Id: I297ff7f3c8e725c24c7f7687786c784f61f5d4e2
fc8603a499