network/simulation: change PropertyBootnode to const

Author: chadsr

network/simulation/node.go

@@ -35,13 +35,15 @@ import (
 	"github.com/ethersphere/swarm/network"
 )
 
-var (
-	BucketKeyBzzPrivateKey BucketKey = "bzzprivkey"
-
+const (
 	// PropertyBootnode is a property string for NodeConfig, representing that a node is a bootnode
 	PropertyBootnode = "bootnode"
 )
 
+var (
+	BucketKeyBzzPrivateKey BucketKey = "bzzprivkey"
+)
+
 // NodeIDs returns NodeIDs for all nodes in the network.
 func (s *Simulation) NodeIDs() (ids []enode.ID) {
 	nodes := s.Net.GetNodes()