Let unmounting succeed when pvc is not mounted
We just had a situation where the driver tried to unmount a pvc that was in fact not mounted, for reasons that we do not fully understand. It may have been related to restarts of the cluster workers via
yiic running on a stale cosmos2 deployment (management), which has resulted in broken api keys on at least some nodes.
In such a situation, it is probably better for the driver to detect this and return a positive result, while logging a big warning that this is not normal behaviour.