remove re-export of parking_lot in util (#6435)

sync/src/tests/helpers.rs

@@ -16,6 +16,7 @@
 
 use std::collections::{VecDeque, HashSet, HashMap};
 use std::sync::Arc;
+use parking_lot::RwLock;
 use util::*;
 use network::*;
 use tests::snapshot::*;

sync/src/tests/snapshot.rs

@@ -17,6 +17,7 @@
 use std::collections::HashMap;
 use std::sync::Arc;
 use hash::keccak;
+use parking_lot::Mutex;
 use util::*;
 use ethcore::snapshot::{SnapshotService, ManifestData, RestorationStatus};
 use ethcore::header::BlockNumber;