The discardChanges function should not be recursive.

For example: 
````kotlin
val department = Departments.findById(1) ?: return
department.name = "tech"

val employee = Employee()
employee.department = department
employee.name = "vince"
Employees.add(employee)

department.location = "Guangzhou"
department.flushChanges()
````

Then we will lost the update of `department.name = "tech"` unexpectedly.