nixos/tests/hibernate: disable for platforms other than x86_64
nixos/tests/hibernate: disable for platforms other than x86_64

Due to 9pnet_virtio bugs, /nix is no longer available after
hibernation. It happens to work on x86_64, but not on other
platforms.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs