Send the bus's user list alone before a walk's gate, so a new grant is on the bus when the first machine is judged (issue 490)

A walk left the machine holding the bus out of a gated send whenever a
build waited there for that same gate, so a module's new health tool was
refused by the bus on its first machine and the gate could not pass. The
grants step sends that machine its declaration with every build kept,
before the first machine's send; plans and the change plan say it.

cmd/mesh-controller/gate.go

@@ -1353,6 +1353,10 @@ func gateLine(g *inventory.PlanGate) string {
 	if g.Rollback != "" {
 		line += "; " + g.Rollback
 	}
+	// Before the send it judges (novox/hq issue 490).
+	if said := grantsSaid(g.Grants); said != "" {
+		line += "; " + said
+	}
 	return line
 }