Remove useless use crate_name; imports.

A `crate_name::foo` path always works in 2018

components/net/tests/cookie.rs

@@ -2,7 +2,6 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-use cookie_rs;
 use net::cookie::Cookie;
 use net::cookie_storage::CookieStorage;
 use net_traits::CookieSource;

components/net/tests/hsts.rs

@@ -5,7 +5,6 @@
 use net::hsts::{HstsEntry, HstsList};
 use net_traits::IncludeSubdomains;
 use std::collections::HashMap;
-use time;
 
 #[test]
 fn test_hsts_entry_is_not_expired_when_it_has_no_timestamp() {

components/net/tests/http_cache.rs

@@ -11,7 +11,6 @@ use net_traits::request::{Destination, Request, RequestInit};
 use net_traits::response::{Response, ResponseBody};
 use servo_url::ServoUrl;
 use std::sync::mpsc::channel;
-use time;
 
 
 #[test]