Remove and sort usings

Author: dingmeng-xue

src/Common/AzurePSCmdlet.cs

@@ -20,12 +20,10 @@
 using Microsoft.WindowsAzure.Commands.Common.CustomAttributes;
 using System;
 using System.Collections.Concurrent;
-using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Management.Automation;
-using System.Management.Automation.Runspaces;
 using System.Text;
 
 namespace Microsoft.WindowsAzure.Commands.Utilities.Common