Vulkan: Fix perftests null driver. We needed to set the CWD for the mock ICD as well. Bug: angleproject:2604 Change-Id: I1d285c478030056360fd2dceca78e231ac321219 Reviewed-on: https://chromium-review.googlesource.com/1169426 Reviewed-by: Omar El Sheikh <theoking@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>