Put the Vulkan layer JSON files in the same place as the gn build puts
them, for consistency.

Change-Id: I6294372ce34ed20da357a8b8ea83018c4e748c37
Reviewed-on: https://chromium-review.googlesource.com/475074Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>