Update Vulkan README
Update Vulkan README

Update references to the mustpass location,
parameterize package name.

Components: Vulkan

VK-GL-CTS issue: 759

Change-Id: I4f15a1aa5eb54ad4b11e3b7a3a5a391fe81b9dac

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