Use the correct way to iterate over an array

See https://github.com/strongloop/loopback-datasource-juggler/issues/512

lib/model-builder.js

@@ -720,7 +720,7 @@ ModelBuilder.prototype.buildModels = function (schemas, createModel) {
   }
 
   var relations = [];
-  for (var s in schemas) {
+  for (var s = 0, n = schemas.length; s < n; s++) {
     var name = this.getSchemaName(schemas[s].name);
     schemas[s].name = name;
     var model;