dra kubelet: fix error log

Previously we were returning the error string from 'err' (which is nil), when
we should have been returning it from result.Error. Without this it is hard to
debug issues with NodeUnprepareResources.

Signed-off-by: Kevin Klues <kklues@nvidia.com>

pkg/kubelet/cm/dra/manager.go

@@ -380,7 +380,7 @@ func (m *ManagerImpl) UnprepareResources(pod *v1.Pod) error {
 				return fmt.Errorf("NodeUnprepareResources returned result for unknown claim UID %s", claimUID)
 			}
 			if result.Error != "" {
-				return fmt.Errorf("NodeUnprepareResources failed for claim %s/%s: %s", reqClaim.Namespace, reqClaim.Name, err)
+				return fmt.Errorf("NodeUnprepareResources failed for claim %s/%s: %s", reqClaim.Namespace, reqClaim.Name, result.Error)
 			}
 
 			// Delete last pod UID only if unprepare succeeds.