* Add Unit Test demonstrating the issue
This test demonstrates a panic that occurs when the user inserts an
item with an instant in the past, and then tries to reset the timeout
using the returned key
* Guard reset_at against removals of expired items
Trying to remove an already expired Timer Wheel entry (called by
DelayQueue.reset()) causes panics in some cases as described in (#2573)
This prevents this panic by removing the item from the expired queue and
not the wheel in these cases
Fixes: #2473
