Edited Issue: ApiExplorer not returning descriptions in certain scenarios [1213]

__Scenario__:
User is trying to use UriPathExtensionMappings along with attribute routing. User would like to see the the appropriate information on the HelpPage(which uses ApiExplorer behind the scenes).

__Issue__:
For the following controller and actions, ApiExplorer does not return any descriptions.

```
[RoutePrefix("api/values")]
public class ValuesController : ApiController
{
[HttpGet("")]
[HttpGet("~/api/values.{ext}")]
public IEnumerable<string> GetAll1()
{
return new string[] { Configuration.Services.GetApiExplorer().ApiDescriptions.Count.ToString() };
}

[HttpGet("path1")]
[HttpGet("path2")]
public IEnumerable<string> GetAll2()
{
return new string[] { "value1", "value2" };
}

}

```

__NOTE__: While trying to repro the above issue, you might hit the # 865 for GetAll1 method.

__Attached__ a standalone katana selfhost repro.

__Expected__: count should be 4
__Actual__: count is 0