Don't overwrite a custom set HttpClientFactory

An end-user, or unit tests, should be able to set a custom
HttpClientFactory and not have OpenStackNet.Configure() nuke it.

Author: carolynvs

src/corelib/OpenStackNet.cs

@@ -60,13 +60,16 @@ public static void Configure(Action<FlurlHttpConfigurationOptions> configureFlur
 
                 FlurlHttp.Configure(c =>
                 {
-                    // Apply our default settings
-                    c.HttpClientFactory = new AuthenticatedHttpClientFactory();
-
                     // Apply the application's default settings
                     if (configureFlurl != null)
                         configureFlurl(c);
 
+                    //
+                    // Apply our default settings
+                    //
+                    if(c.HttpClientFactory is DefaultHttpClientFactory)
+                        c.HttpClientFactory = new AuthenticatedHttpClientFactory();
+
                     // Apply our event handling without clobbering any application level handlers
                     var applicationBeforeCall = c.BeforeCall;
                     c.BeforeCall = call =>