Pass AuthenticationMode option when using ValidationMode.ValidationEndpoint

[KautskyLozanoV]

I was trying to use OWIN Cookie Authentication for MVC with Active AuthenticationMode and UseIdentityServerBearerTokenAuthentication middleware for WebAPI with Passive AuthenticationMode but this option is never set when using ValidationEndpoint (here)

internal static void UseValidationEndpoint(this IAppBuilder app, IdentityServerBearerTokenAuthenticationOptions options)
        {
            if (options.EnableValidationResultCache)
            {
                if (options.ValidationResultCache == null)
                {
                    options.ValidationResultCache = new InMemoryValidationResultCache(options);
                }
            }

            app.UseOAuthBearerAuthentication(new OAuthBearerAuthenticationOptions
            {
                AccessTokenProvider = new ValidationEndpointTokenProvider(options),
                Provider = options.Provider,
            });
        }

It would be nice to have this options so we could use this middleware on a passive authentication mode

[leastprivilege]

should be fixed on dev / RC2