Add an interface to check the status of paused scheduler. #3052
Description
Feature Request
Describe your feature request related problem
To solve pingcap/br#549, when br pause the scheduler with a specified delay. we only know the request is succeed or not. then it's not easy for br to add integration test to test the status of scheduler.
Describe the feature you'd like
It's better to have an interface to know whether the scheduler paused succeed or not.