Expiration watcher timestamp issue

[kober32]

In WMTOperationExpirationWatcher line 216, the timer needs to be scheduled for +1 second (or otherwise) because it can be fired before the actual expiration. This leads to the operation remaining in the UI.

For example, the timer was scheduled on the exact time of expiration but was fired before:

(lldb) po operationExpires.timeIntervalSince1970
1617645305.0

(lldb) po currentDate.timeIntervalSince1970
1617645304.999485

and since the difference is 0.000514984130859375 (greater than 0), the operation is not expired...