Venus crashes guest if vkCreateInstance is called on MoltenVK
I'm working on integrating virglrenderer with MoltenVK on MacOS. However, I found that when vkCreateInstance is called, even though the instance is successfully created, mesa on the guest crashes, bring down QEMU with it.
Re: Hanging when testing Venus Driver with "stuck in ring seqno wait with iter at"
So... I found the mistake --- I forgot to actually implement the different contexts in `virgl_cmd_context_create`.