ANGLE D3D11: Always execute QueryInterface

ASSERT removes the condition when building for release mode. However,
QueryInterface must be called in any case. Adopt to using ASSERT(false)
like in other occurrences in angle.

This is a follow-up patch to 331bc16afd23414493b842819e0b747e8f364243

Change-Id: I4413bab06b5a529fcbd09bbc20828fcdcf4e4fc6
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Andrew Knight <andrew.knight@digia.com>