Save & restore the state of [Net.ServicePointManager]::SecurityProtoc…

…ol (#240)

[Net.ServicePointManager]::SecurityProtocol is a global configuration that was being modified during the execution of `Invoke-GHRestMethod`.  With this change, the global state will be cached before the change and restored immediately afterwards.

Fixes #230

GitHubCore.ps1

@@ -201,6 +201,7 @@ function Invoke-GHRestMethod
     }
 
     $NoStatus = Resolve-ParameterWithDefaultConfigurationValue -Name NoStatus -ConfigValueName DefaultNoStatus
+    $originalSecurityProtocol = [Net.ServicePointManager]::SecurityProtocol
 
     try
     {
@@ -560,6 +561,10 @@ function Invoke-GHRestMethod
         Set-TelemetryException -Exception $ex -ErrorBucket $errorBucket -Properties $localTelemetryProperties -NoStatus:$NoStatus
         throw $newLineOutput
     }
+    finally
+    {
+        [Net.ServicePointManager]::SecurityProtocol = $originalSecurityProtocol
+    }
 }
 
 function Invoke-GHRestMethodMultipleResult