don't destroy connection until client is finished

lib/dialects/mysql/connector-manager.js

@@ -50,9 +50,20 @@ module.exports = (function() {
   ConnectorManager.prototype.disconnect = function() {
     var self = this
     this.client.end(function() {
-      // needed to prevent mysql connection leak
-      self.client.destroy()
-      self.client = null
+      var intervalObj = null
+      var cleanup = function () {
+        var retryCt = 0
+        // make sure to let client finish before calling destroy
+        if (!self.hasNoConnections) {
+          return
+        }
+        // needed to prevent mysql connection leak
+        self.client.destroy()
+        self.client = null
+        clearInterval(intervalObj)
+      }
+      intervalObj = setInterval(cleanup, 10)
+      cleanup()
     })
   }