Fix SelfSignedCertificateMockServer code analysis errors (#5739)

Author: jeffkl

test/TestUtilities/Test.Utility/SelfSignedCertificateMockServer.cs

@@ -7,7 +7,6 @@
 using System.Net;
 using System.Net.Security;
 using System.Net.Sockets;
-using System.Security.Authentication;
 using System.Security.Cryptography;
 using System.Security.Cryptography.X509Certificates;
 using System.Text;
@@ -18,7 +17,7 @@
 
 namespace Test.Utility
 {
-    public class SelfSignedCertificateMockServer
+    public class SelfSignedCertificateMockServer : IDisposable
     {
         private readonly X509Certificate2 _certificate;
         private readonly string _packageDirectory;
@@ -199,6 +198,17 @@ private static X509Certificate2 GenerateSelfSignedCertificate()
                 return new X509Certificate2(certBytes, "password", X509KeyStorageFlags.Exportable);
             }
         }
+
+        public void Dispose()
+        {
+            _tcpListener.Stop();
+
+#if NET8_0_OR_GREATER
+            _tcpListener.Dispose();
+#endif
+
+            _certificate.Dispose();
+        }
     }
 
     internal class Resource