test: fix test failure in MySQL connector

Fix a test using a string Person.id value to use a numeric value
instead, in order to support connectors that use numeric ids by default.

test/manipulation.test.js

@@ -617,7 +617,7 @@ describe('manipulation', function () {
 
     it('should allow save() of the created instance', function(done) {
       Person.updateOrCreate(
-        { id: 'new-id', name: 'a-name' },
+        { id: 999 /* a new id */, name: 'a-name' },
         function(err, inst) {
           if (err) return done(err);
           inst.save(done);