This enables these tests for Vulkan:
dEQP-GLES2.functional.fragment_ops.depth.*
dEQP-GLES2.functional.fragment_ops.stencil.*

Bug: angleproject:2430

Change-Id: I5c58821ac2f84ce9ae5a92b3024853e5b85ad41e
Reviewed-on: https://chromium-review.googlesource.com/981999
Commit-Queue: Luc Ferron <lucferron@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>