Edited Issue: [AttributeRouting]Parsing error when using paranthesis in the route template's default values [978]

For the following action:

Note: the default value is a guid enclosed { , } characters.
```
[HttpGet("ForGuids/v3/{id:guid={6A9B7F3B-ED68-4759-ABBA-959ED47EB326}}")]
public string ForGuids(Guid id)
{
return "ForGuids:" + id.ToString();
}
```

Following error is thrown during configuration:

_System.ArgumentException : There is an incomplete parameter in this path segment: '{id}}'. Check that each '{' character has a matching '}' character.
Parameter name: routeTemplate

at System.Web.Http.Routing.HttpRouteParser.Parse(String routeTemplate) in c:\WebstackRuntime\Runtime\src\System.Web.Http\Routing\HttpRouteParser.cs:line 102
at System.Web.Http.Routing.HttpRoute..ctor(String routeTemplate, HttpRouteValueDictionary defaults, HttpRouteValueDictionary constraints, HttpRouteValueDictionary dataTokens, HttpMessageHandler handler) in c:\WebstackRuntime\Runtime\src\System.Web.Http\Routing\HttpRoute.cs:line 68
at System.Web.Http.Routing.HttpRoute..ctor(String routeTemplate, HttpRouteValueDictionary defaults, HttpRouteValueDictionary constraints) in c:\WebstackRuntime\Runtime\src\System.Web.Http\Routing\HttpRoute.cs:line 49
at System.Web.Http.Routing.HttpRouteBuilder.BuildHttpRoute(HttpRouteValueDictionary defaults, HttpRouteValueDictionary constraints, String routeTemplate) in c:\WebstackRuntime\Runtime\src\System.Web.Http\Routing\HttpRouteBuilder.cs:line 111
at System.Web.Http.Routing.HttpRouteBuilder.BuildHttpRoute(String routeTemplate, IEnumerable`1 httpMethods, String controllerName, String actionName) in c:\WebstackRuntime\Runtime\src\System.Web.Http\Routing\HttpRouteBuilder.cs:line 99
at System.Web.Http.HttpConfigurationExtensions.CreateAttributeRoutes(HttpRouteBuilder routeBuilder, String controllerName, Collection`1 routePrefixes, IGrouping`2 actionGrouping) in c:\WebstackRuntime\Runtime\src\System.Web.Http\HttpConfigurationExtensions.cs:line 143
at System.Web.Http.HttpConfigurationExtensions.MapHttpAttributeRoutes(HttpConfiguration configuration, HttpRouteBuilder routeBuilder) in c:\WebstackRuntime\Runtime\src\System.Web.Http\HttpConfigurationExtensions.cs:line 90
at System.Web.Http.HttpConfigurationExtensions.MapHttpAttributeRoutes(HttpConfiguration configuration) in c:\WebstackRuntime\Runtime\src\System.Web.Http\HttpConfigurationExtensions.cs:line 59
at WebStack.QA.Tests.AttributeRouting.DefaultValuesTest.UpdateConfiguration(HttpConfiguration config) in c:\WebstackRuntime\QA\Func\src\MainTests\Tests\AttributeRouting\DefaultValuesTest.cs:line 35_