Broker pallet: RegionDropped event fix & additional tests (#1609)

This PR includes the following fix:
- [x] The `duration` is always set to zero in the `RegionDropped` event.
This is fixed in this PR.

Also added some additional tests to cover some cases that aren't covered
:
- [x] Selling a partitioned region to the instantaneous coretime pool.
- [x] Partitioning a region after assigning it to a particular task.
- [x] Interlacing a region after assigning it to a particular task.

substrate/frame/broker/src/dispatchable_impls.rs

@@ -76,7 +76,7 @@ impl<T: Config> Pallet<T> {
 			last_timeslice: Self::current_timeslice(),
 		};
 		let now = frame_system::Pallet::<T>::block_number();
-		let dummy_sale = SaleInfoRecord {
+		let new_sale = SaleInfoRecord {
 			sale_start: now,
 			leadin_length: Zero::zero(),
 			price,
@@ -89,7 +89,7 @@ impl<T: Config> Pallet<T> {
 			cores_sold: 0,
 		};
 		Self::deposit_event(Event::<T>::SalesStarted { price, core_count });
-		Self::rotate_sale(dummy_sale, &config, &status);
+		Self::rotate_sale(new_sale, &config, &status);
 		Status::<T>::put(&status);
 		Ok(())
 	}