demos: Change cube to use FIFO present mode
demos: Change cube to use FIFO present mode

And throttle using fences

Change-Id: I13cd622f9a401fdb44bf7b74343589b70e340b77

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools