GCE Multizone: Allow volumes to be created in non-master zone
GCE Multizone: Allow volumes to be created in non-master zone

We had a long-lasting bug which prevented creation of volumes in
non-master zones, because the cloudprovider in the volume label
admission controller is not initialized with the multizone setting
(issue #27656).

This implements a simple workaround: if the volume is created with the
failure-domain zone label, we look for the volume in that zone.  This is
more efficient, avoids introducing a new semantic, and allows users (and
the dynamic provisioner) to create volumes in non-master zones.

Fixes #27657

kubernetes/cloud-provider-gcp,kubernetes/cloud-provider-gcp