fix(Mongoose): fix connection setter

Author: jinasonlin

lib/index.js

@@ -528,7 +528,10 @@ Mongoose.prototype.__defineGetter__('connection', function() {
 });
 
 Mongoose.prototype.__defineSetter__('connection', function(v) {
-  this.connections[0] = v;
+  if (v instanceof Connection) {
+    this.connections[0] = v;
+    this.models = v.models;
+  }
 });
 
 /*!