Avoid boxing in IEndpointResolverExtensions.cs

Technically T can be a value type. `Object.Equals` has an overload that takes `object` therefore any struct would be boxed. To avoid it, `EqualityComparer<T>.Default.Equals` should be used.

Author: lechu445

projects/RabbitMQ.Client/client/api/IEndpointResolverExtensions.cs

@@ -71,7 +71,7 @@ public static async Task<T> SelectOneAsync<T>(this IEndpointResolver resolver,
                 }
             }
 
-            if (Object.Equals(t, default(T)) && exceptions.Count > 0)
+            if (EqualityComparer<T>.Default.Equals(t, default(T)) && exceptions.Count > 0)
             {
                 throw new AggregateException(exceptions);
             }