treewide: initialize empty structs with var

Change-Id: I72d3993eaf5fe57c77b1dda8218e36a8cc11813d
Reviewed-on: https://review.monogon.dev/c/monogon/+/3108
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/metropolis/node/kubernetes/reconciler/reconciler_status.go b/metropolis/node/kubernetes/reconciler/reconciler_status.go
index f3ad06b..4abf6f8 100644
--- a/metropolis/node/kubernetes/reconciler/reconciler_status.go
+++ b/metropolis/node/kubernetes/reconciler/reconciler_status.go
@@ -194,7 +194,7 @@
 		if len(kv.Value) == 0 {
 			return
 		}
-		node := ppb.Node{}
+		var node ppb.Node
 		if err := proto.Unmarshal(kv.Value, &node); err != nil {
 			supervisor.Logger(ctx).Errorf("Failed to unmarshal node %q: %w", nodeKey, err)
 			return