ProvisionSelinux: try to remove nix module only if it's already installed#1733

cole-h wants to merge 1 commit intomainDeterminateSystems/nix-installer:mainfrom

only-remove-selinux-module-if-actually-installedDeterminateSystems/nix-installer:only-remove-selinux-module-if-actually-installedCopy head branch name to clipboard