refactor: drop superfluous return value

Now that group summary rendering always produce something, it no
longer needs to indicate whether it did

render/detailed/summary.go

@@ -114,8 +114,8 @@ func MakeNodeSummary(rc report.RenderContext, n report.Node) (NodeSummary, bool)
 		return summary, true
 	}
 	if strings.HasPrefix(n.Topology, "group:") {
-		summary, b := groupNodeSummary(baseNodeSummary(r, n), r, n)
-		return RenderMetricURLs(summary, n, rc.MetricsGraphURL), b
+		summary := groupNodeSummary(baseNodeSummary(r, n), r, n)
+		return RenderMetricURLs(summary, n, rc.MetricsGraphURL), true
 	}
 	return NodeSummary{}, false
 }
@@ -348,7 +348,7 @@ func weaveNodeSummary(base NodeSummary, n report.Node) NodeSummary {
 
 // groupNodeSummary renders the summary for a group node. n.Topology is
 // expected to be of the form: group:container:hostname
-func groupNodeSummary(base NodeSummary, r report.Report, n report.Node) (NodeSummary, bool) {
+func groupNodeSummary(base NodeSummary, r report.Report, n report.Node) NodeSummary {
 	base.Label, base.Rank = n.ID, n.ID
 	if topology, _, ok := render.ParseGroupNodeTopology(n.Topology); ok {
 		if t, ok := r.Topology(topology); ok {
@@ -359,7 +359,7 @@ func groupNodeSummary(base NodeSummary, r report.Report, n report.Node) (NodeSum
 		}
 	}
 	base.Stack = true
-	return base, true
+	return base
 }
 
 func pluralize(counters report.Counters, key, singular, plural string) string {