Close milestone database when calling Backend.close

Author: Alec Gibson

lib/backend.js

@@ -107,7 +107,7 @@ Backend.prototype._shimAfterSubmit = function() {
 };
 
 Backend.prototype.close = function(callback) {
-  var wait = 3;
+  var wait = 4;
   var backend = this;
   function finish(err) {
     if (err) {
@@ -119,6 +119,7 @@ Backend.prototype.close = function(callback) {
   }
   this.pubsub.close(finish);
   this.db.close(finish);
+  this.milestoneDb.close(finish);
   for (var name in this.extraDbs) {
     wait++;
     this.extraDbs[name].close(finish);