Only update the game list when there may be changes to it.

When just starting and stopping emulation, just hide/show it,
but only if necessary because we are rendering to the main window.

Fixes issue 3460.


git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@6889 8ced0084-cf51-0410-be5f-012b33b47a6e