NODE-899 Avoid any cyclic dependency so marshalling does not break if using JSON.stringify

Author: christkv

lib/collection.js

@@ -899,7 +899,7 @@ var updateOne = function(self, filter, update, options, callback) {
 
     // Fix for NODE-899, backward compatibility with legacy format
     if(r.upsertedId) {
-      r.upsertedId._id = r.upsertedId;
+      r.upsertedId._id = new ObjectID(r.upsertedId.id);
     }
 
     if(callback) callback(null, r);

test/functional/crud_api_tests.js

@@ -538,6 +538,7 @@ exports['should correctly execute update methods using crud api'] = {
             test.ok(r.upsertedId != null);
             test.equal('ObjectID', r.upsertedId._bsontype);
             test.equal('ObjectID', r.upsertedId._id._bsontype);
+            test.equal(r.upsertedId.toHexString(), r.upsertedId._id.toHexString());
 
             db.collection('t3_2').updateOne({ c: 1 }
               , { $set: { a: 1 } }, function(err, r) {