Since we are only interested in the difference to non-default states,
bindings with a zero ID should not be serialized.

This resolves the comparision error in the GetTexLevelParameterTest.*
tests. The test now do not need to be skipped.

Bug: angleproject:5645
Change-Id: I887bc22b52a201c467c00c42f6ddb3b38895a7c4
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2739726Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Commit-Queue: Lubosz Sarnecki <lubosz.sarnecki@collabora.com>