Autostart config doesn't allow for shared storage of VM files

[Steve Prior]

As others have done I have several virtualbox servers which store the VM definitions on a common NFS share to facilitate rebalancing loads, maintenance, and teleportation. The current implementation of autostart uses a config entry in the VM definition .vbox file to determine whether the machine should autostart, but that won't work in the case where the machine definition has been registered on multiple machines, it'd try to autostart on all of them.

I believe the autostart config should not be stored in the machine config file, but in the ~/.VirtualBox directory which can still be specific to the server machine even though the VM definition is shared across servers.