Vulkan: Clear surface images if emulated format This was done for renderbuffers but was missing for surfaces. Bug: angleproject:2722 Change-Id: I019805d6ca43eef86d2d46e7c72c1013803f2139 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1570149 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>