nixos/virtualbox: Revert disable hardening.

This reverts commit 5d67b17901ff2c9a18647bd9453c6b0d4294b875.

The issues have been resolved by ac603e208c98b260db675fa0c13be94fa95216f4.

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>