Mid-render-pass clears (through UtilsVk) run on the current subpass,
which in the presence of multisampled-render-to-texture unresolve
would be subpass 1.  The graphics pipeline for that draw call should
set the correct subpass index.

Bug: angleproject:4836
Change-Id: Iba4a03ea96a63b0f5d09c27e5283ff8a8b534e05
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2441509
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>