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

dapps/src/tests/helpers/fetch.rs

@@ -16,7 +16,7 @@
 
 use std::{io, thread, time};
 use std::sync::{atomic, mpsc, Arc};
-use util::Mutex;
+use parking_lot::Mutex;
 
 use futures::{self, Future};
 use fetch::{self, Fetch};

dapps/src/tests/helpers/registrar.rs

@@ -20,7 +20,8 @@ use std::collections::HashMap;
 use rustc_hex::FromHex;
 
 use hash_fetch::urlhint::ContractClient;
-use util::{Bytes, Address, Mutex, H256, ToPretty};
+use parking_lot::Mutex;
+use util::{Bytes, Address, H256, ToPretty};
 
 const REGISTRAR: &'static str = "8e4e9b13d4b45cb0befc93c3061b1408f67316b2";
 const URLHINT: &'static str = "deadbeefcafe0000000000000000000000000000";