属性の方はpersistence.xmlより優先である！
下記は説明：
public static EntityManagerFactory createEntityManagerFactory(java.lang.String persistenceUnitName,
java.util.Map properties)Create and return an EntityManagerFactory for the named persistence unit using the given properties.
Parameters:
persistenceUnitName - the name of the persistence unit
properties - Additional properties to use when creating the factory. The values of these properties override any values that may have been configured elsewhere.