Adding help for chef cmdlets


<!---@tfsbridge:{"tfsId":2307482}-->
Please move using above the namespace like such:
```csharp
    using System.Collections.Generic;
    using System.Linq;
    using Commands.Test.Utilities.Common;
    using ServiceManagement.IaaS.Extensions;
    using VisualStudio.TestTools.UnitTesting;
    using Microsoft.WindowsAzure.Commands.Utilities;
    using System.Management.Automation;
    using Model;
    namespace Microsoft.WindowsAzure.Commands.ServiceManagement.Test.UnitTests.Cmdlets.IaaS.Extensions
    {
    ....
```