Use the workQueue.

Author: johnno1962

Foundation/URLSession/URLSession.swift

@@ -190,7 +190,6 @@ open class URLSession : NSObject {
     fileprivate var nextTaskIdentifier = 1
     internal let workQueue: DispatchQueue 
     internal let taskRegistry = URLSession._TaskRegistry()
-    fileprivate let identiferLock = NSLock()
     fileprivate let identifier: Int32
     fileprivate var invalidated = false
     fileprivate static let registerProtocols: () = {