Revise according to review

Author: dingmeng-xue

src/Network/Network/PrivateLinkService/GetAzurePrivateLinkServiceCommand.cs

@@ -19,7 +19,7 @@
 using System.Management.Automation;
 using Microsoft.Rest.Azure;
 using Microsoft.Azure.Commands.ResourceManager.Common.ArgumentCompleters;
-
+using NM = Microsoft.Azure.Management.Network.Models;
 
 namespace Microsoft.Azure.Commands.Network
 {
@@ -75,7 +75,7 @@ public override void Execute()
             }
             else 
             {
-                IPage<Microsoft.Azure.Management.Network.Models.PrivateLinkService> plsPage;
+                IPage<NM.PrivateLinkService> plsPage;
                 if (ShouldListByResourceGroup(ResourceGroupName, Name))
                 {
                     plsPage = this.PrivateLinkServiceClient.List(this.ResourceGroupName);
@@ -86,7 +86,7 @@ public override void Execute()
                 }
 
 
-                var plsList = ListNextLink<Microsoft.Azure.Management.Network.Models.PrivateLinkService>.GetAllResourcesByPollingNextLink(plsPage, this.PrivateLinkServiceClient.ListNext);
+                var plsList = ListNextLink<NM.PrivateLinkService>.GetAllResourcesByPollingNextLink(plsPage, this.PrivateLinkServiceClient.ListNext);
                 var psPLSs = new List<PSPrivateLinkService>();
                 foreach (var pls in plsList)
                 {

src/Network/Network/PrivateLinkService/PrivateLinkServiceProvider/GenericProvider.cs

@@ -22,7 +22,7 @@
 
 namespace Microsoft.Azure.Commands.Network.PrivateLinkService.PrivateLinkServiceProvider
 {
-    public class GenericProvider : IPrivateLinkProvider
+    internal class GenericProvider : IPrivateLinkProvider
     {
 
         private static IDictionary<string, string> _apiVersions = new Dictionary<string, string>{

src/Network/Network/PrivateLinkService/PrivateLinkServiceProvider/PrivateLinkProviderFactory.cs

@@ -14,7 +14,7 @@
 
 namespace Microsoft.Azure.Commands.Network.PrivateLinkService.PrivateLinkServiceProvider
 {
-    public class PrivateLinkProviderFactory
+    internal class PrivateLinkProviderFactory
     {
         private const string NETWORKING_TYPE = "microsoft.network/privatelinkservices";