We adapt the existing code to work across all zones in a region.
We require a feature-flag to enable Ubernetes-Lite
Reasons:
* There are some behavioural changes if users create volumes with
the same name in two zones.
* We don't want to make one API call per zone if we're not running
Ubernetes-Lite.
* Ubernetes-Lite is still experimental.
There isn't a parallel flag implemented for AWS, because at the moment
there would be no behaviour changes from this.
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