uncomment 4.9 upgrade code (#8582)

* set db to 4.9

* add prepatory code for 4.10

* bug from old example

model/version.go

@@ -13,6 +13,7 @@ import (
 // It should be maintained in chronological order with most current
 // release at the front of the list.
 var versions = []string{
+	"4.9.0",
 	"4.8.1",
 	"4.8.0",
 	"4.7.2",