Vulkan: Fix issue with redefining a layered attachment. The fix ensures we complete level redefinition before we get the layer render target in TextureVk::getAttachmentRenderTarget. Bug: chromium:1296866 Change-Id: Id7fa8e9fed5e766c30580b09336713c675c4e4f0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3498283 Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>