The DetachDisk method of AWS cloudprovider indirectly calls
EC2::DescribeVolume AWS API function to check if the volume
being detached is really attached to the specified node.
The AWS API call may fail and return error which is logged however
the DetachDisk then finishes successfully. This may cause the AWS
volumes to remain attached to the instances forever because the
attach/detach controller will mark the volume as attached. The PV
controller will never be able to delete those disks and they need
to be detached manually.
This patch ensures on error from DescribeVolume is propagated to
attach/detach controller and the detach operation is re-tried.
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