kvserver: fix delegated snap gen change error

When the range descriptor of the delegate is lower than the descriptor
generation of the delegating replica (leaseholder), the store returns an error,
which is also logged (v=2).

The error message mixed up the delegating and delegated replica's
generation. Swap them around.

Epic: none
Release note: None

Author: kvoli

pkg/kv/kvserver/replica_command.go

@@ -2935,14 +2935,12 @@ func (r *Replica) validateSnapshotDelegationRequest(
 	// snapshot will still be valid since the leaseholder is also on this
 	// generation by now.
 	if desc.Generation < req.DescriptorGeneration {
-		log.VEventf(ctx, 2,
+		err := errors.Errorf(
 			"%s: generation has changed since snapshot was generated %s < %s",
-			r, req.DescriptorGeneration, desc.Generation,
-		)
-		return errors.Errorf(
-			"%s: generation has changed since snapshot was generated %s < %s",
-			r, req.DescriptorGeneration, desc.Generation,
+			r, desc.Generation, req.DescriptorGeneration,
 		)
+		log.VEventf(ctx, 2, "%v", err)
+		return err
 	}
 
 	// Check that the snapshot we generated has a descriptor that includes the