(GH-719) Reset ServerCertificateValidationCallback

If the server certificate validation callback is set in
ServicePointManager, reset it to null with a warning.

src/chocolatey/infrastructure.app/services/PowershellService.cs

@@ -31,6 +31,7 @@ namespace chocolatey.infrastructure.app.services
     using cryptography;
     using domain;
     using infrastructure.commands;
+    using infrastructure.registration;
     using logging;
     using NuGet;
     using powershell;
@@ -468,6 +469,8 @@ public void prepare_powershell_environment(IPackage package, ChocolateyConfigura
                     Environment.SetEnvironmentVariable("CacheChecksumType_{0}".format_with(urlKey), "sha512");
                 }
             }
+
+            SecurityProtocol.set_protocol();
         }
 
         private ResolveEventHandler _handler = null;

src/chocolatey/infrastructure/registration/SecurityProtocol.cs

@@ -50,6 +50,20 @@ Chaining. Upgrade to at least .NET 4.5 at your earliest convenience.
  For more information you should visit https://www.howsmyssl.com/");
 
             }
+
+            try
+            {
+                if (ServicePointManager.ServerCertificateValidationCallback != null)
+                {
+                    "chocolatey".Log().Warn("ServerCertificateValidationCallback was set to '{0}' Removing.".format_with(System.Net.ServicePointManager.ServerCertificateValidationCallback));
+                    ServicePointManager.ServerCertificateValidationCallback = null;
+                }
+            }
+            catch (Exception ex)
+            {
+                "chocolatey".Log().Warn("Error resetting ServerCertificateValidationCallback: {0}".format_with(ex.Message));
+            }
+
         }
     }
 }