fix versions for kind cluster creation

Author: chanwit

cmd/ekz/create_cluster_kind.go

@@ -15,11 +15,11 @@ func createClusterKIND() error {
 
 	var buildNo string
 	switch eksdVersion {
-	case "v1.18.16-eks-1-18-5":
+	case V1_18_Image:
 		buildNo = "0"
-	case "v1.19.8-eks-1-19-4":
+	case V1_19_Image:
 		buildNo = "0"
-	case "v1.20.4-eks-1-20-1":
+	case V1_20_Image:
 		buildNo = "0"
 	}