vergil: fix automatic mount ambiguity.

hosts/vergil/configuration.nix

@@ -1,4 +1,8 @@
-{ pkgs, ... }:
+{ pkgs, utils, ... }:
+let
+  disk = "/dev/storage/vm-100-disk-0";
+  diskDevice = "${utils.escapeSystemdPath disk}.device";
+in
 {
   imports = [
     ../shared/nixos-server.nix
@@ -7,14 +11,14 @@
 
   systemd.services.mount-vm-disk = {
     description = "Mount Proxmox VM disk via kpartx";
-    after = [ "storage-vm--100--disk--0.device" ];
-    wants = [ "storage-vm--100--disk--0.device" ];
+    requires = [ diskDevice ];
+    after = [ diskDevice ];
 
     serviceConfig = {
       Type = "oneshot";
       RemainAfterExit = true;
-      ExecStart = "${pkgs.multipath-tools}/sbin/kpartx -av /dev/storage/vm-100-disk-0";
-      ExecStop = "${pkgs.multipath-tools}/sbin/kpartx -dv /dev/storage/vm-100-disk-0";
+      ExecStart = "${pkgs.multipath-tools}/sbin/kpartx -av ${disk}";
+      ExecStop = "${pkgs.multipath-tools}/sbin/kpartx -dv ${disk}";
     };
 
     wantedBy = [ "multi-user.target" ];