e2e: more reliable method for selecting node to inject evidence (#6880)

In retrospect my previous implementation of this node, could get
unlucky and never find the correct node. This method is more reliable.

test/e2e/runner/evidence.go

@@ -32,8 +32,9 @@ func InjectEvidence(testnet *e2e.Testnet, amount int) error {
 	// select a random node
 	var targetNode *e2e.Node
 
-	for i := 0; i < len(testnet.Nodes)-1; i++ {
-		targetNode = testnet.Nodes[rand.Intn(len(testnet.Nodes))] // nolint: gosec
+	for _, idx := range rand.Perm(len(testnet.Nodes)) {
+		targetNode = testnet.Nodes[idx]
+
 		if targetNode.Mode == e2e.ModeSeed {
 			targetNode = nil
 			continue