Avoid accessing uninitialized values in get/setPixDepth/Stencil
Avoid accessing uninitialized values in get/setPixDepth/Stencil

Access only depth or stencil component when using combined formats in
tcu::Texture to avoid propagating uninitialized values.

Change-Id: I399c912ef07710a5dbb9e85559d108b98a9f2178

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