vmTools: fix phases
vmTools: fix phases

These gave missing attribute errors.  They should have been written as
strings in ae9337179b7.

Fixes: ae9337179b7 ("vm: deprecate phases")
Fixes: 52b10ee8725 ("vmTools refactor: don't use huge `with pkgs;`")

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