lint fixes to cluster behavior in utils test

This is more lint fixes, but it's less obvious to me what the
right handling for errors is, or whether disregarding them is
safe, so it's a separate commit.

utils_internal_test.go

@@ -235,7 +235,9 @@ func (t *ClusterCluster) addCluster(i int, saveTopology bool) (*cluster, error)
 	// add nodes
 	if saveTopology {
 		for _, n := range t.common.Nodes {
-			c.addNode(n)
+			if err := c.addNode(n); err != nil {
+				return nil, err
+			}
 		}
 	}
 
@@ -314,7 +316,10 @@ func (b bcast) SendSync(m Message) error {
 		// Apply the send message to all nodes (except the coordinator).
 		for _, c := range b.t.Clusters {
 			if c != b.c {
-				c.mergeClusterStatus(obj)
+				err := c.mergeClusterStatus(obj)
+				if err != nil {
+					return err
+				}
 			}
 		}
 		b.t.mu.RLock()
@@ -348,7 +353,9 @@ func (b bcast) SendTo(to *Node, m Message) error {
 		}
 	case *ResizeInstructionComplete:
 		coord := b.t.clusterByID(to.ID)
-		go coord.markResizeInstructionComplete(obj)
+		// this used to be async, but that prevented us from checking
+		// its error status...
+		return coord.markResizeInstructionComplete(obj)
 	case *ClusterStatus:
 		// Apply the send message to the node.
 		for _, c := range b.t.Clusters {