CP: Remove two read-backs from copy image tests
CP: Remove two read-backs from copy image tests

Cherry pick commit b2fb8ad5ceefe26964101bd403e7786ae83274a9
from master.

Bug: 33965234

Remove two read-backs from copy image tests

Test: Ran copy_image on N6 & N9 with L MR1 image to check for
false-negatives. PixelC and Pixel XL for passing with current OS image.

Change-Id: I9f7028eb550012f8d9abe2f7afee2d1402f5abf3

KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,chadversary/deqp,KhronosGroup/VK-GL-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,KhronosGroup/VK-GL-CTS,chadversary/deqp,chadversary/deqp,KhronosGroup/VK-GL-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/Vulkan-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,chadversary/deqp