Revert "nixos/containers: add unprivileged option"

nixos/modules/virtualisation/containers.nix

@@ -139,7 +139,6 @@ let
         --bind="/nix/var/nix/profiles/per-container/$INSTANCE:/nix/var/nix/profiles" \
         --bind="/nix/var/nix/gcroots/per-container/$INSTANCE:/nix/var/nix/gcroots" \
         ${optionalString (!cfg.ephemeral) "--link-journal=try-guest"} \
-        ${optionalString (cfg.unprivileged) "-U"} \
         --setenv PRIVATE_NETWORK="$PRIVATE_NETWORK" \
         --setenv HOST_BRIDGE="$HOST_BRIDGE" \
         --setenv HOST_ADDRESS="$HOST_ADDRESS" \
@@ -239,8 +238,8 @@ let
     ExecReload = pkgs.writeScript "reload-container"
       ''
         #! ${pkgs.runtimeShell} -e
-        ${pkgs.systemd}/bin/machinectl shell "$INSTANCE" \
-          ''${SYSTEM_PATH:-/nix/var/nix/profiles/system}/bin/switch-to-configuration test
+        ${pkgs.nixos-container}/bin/nixos-container run "$INSTANCE" -- \
+          bash --login -c "''${SYSTEM_PATH:-/nix/var/nix/profiles/system}/bin/switch-to-configuration test"
       '';
 
     SyslogIdentifier = "container %i";
@@ -424,7 +423,6 @@ let
       extraVeths = {};
       additionalCapabilities = [];
       ephemeral = false;
-      unprivileged = false;
       allowedDevices = [];
       hostAddress = null;
       hostAddress6 = null;
@@ -518,16 +516,6 @@ in
               '';
             };
 
-            unprivileged = mkOption {
-              type = types.bool;
-              default = false;
-              description = ''
-                Run container in unprivileged mode using private users feature of <command>systemd-nspawn</command>.
-                This option is eqvivalent of adding -U parameter to <command>systemd-nspawn</command> command.
-                See <literal>systemd-nspawn(1)</literal> man page for more information.
-              '';
-            };
-
             ephemeral = mkOption {
               type = types.bool;
               default = false;