Vulkan: Fix sync of initially disabled attributes. If an attribute was never enabled or disabled the default state was not properly synced in our implementation. This wasn't caught by currently enabled tests. Those tests are now enabled in VertexAttributeTest. Bug: angleproject:2800 Change-Id: I97c063651911379e16de4ee557d9840782114c54 Reviewed-on: https://chromium-review.googlesource.com/1199724 Reviewed-by: Frank Henigman <fjhenigman@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>