Shutdown the Snapshot Service early (#8658)

* Shutdown the Snapshot Service when shutting down the runner

* Rename `service` to `client_service`

* Fix tests

ethcore/src/snapshot/service.rs

@@ -743,6 +743,10 @@ impl SnapshotService for Service {
 			trace!("Error sending snapshot service message: {:?}", e);
 		}
 	}
+
+	fn shutdown(&self) {
+		self.abort_restore();
+	}
 }
 
 impl Drop for Service {

ethcore/src/snapshot/traits.rs

@@ -54,4 +54,7 @@ pub trait SnapshotService : Sync + Send {
 	/// Feed a raw block chunk to the service to be processed asynchronously.
 	/// no-op if currently restoring.
 	fn restore_block_chunk(&self, hash: H256, chunk: Bytes);
+
+	/// Shutdown the Snapshot Service by aborting any ongoing restore
+	fn shutdown(&self);
 }