nixos/virtualbox: Revert disable hardening.

This reverts commit 5d67b179.

The issues have been resolved by ac603e20

.

Tested this with hostonlyifs and USB support with extension pack.

Conflicts:
	nixos/modules/programs/virtualbox-host.nix

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Tested-by: Mateusz Kowalczyk <fuuzetsu@fuuzetsu.co.uk>