nixos/pam: refactor pam_mount unmounting fix

nixos/modules/security/pam.nix

@@ -611,7 +611,6 @@ let
             session optional ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so
           '' +
           optionalString cfg.pamMount ''
-            session [success=1 default=ignore] ${pkgs.pam}/lib/security/pam_succeed_if.so service = systemd-user quiet
             session optional ${pkgs.pam_mount}/lib/security/pam_mount.so disable_interactive
           '' +
           optionalString use_ldap ''

nixos/modules/system/boot/systemd/user.nix

@@ -145,6 +145,10 @@ in {
       { # Ensure that pam_systemd gets included. This is special-cased
         # in systemd to provide XDG_RUNTIME_DIR.
         startSession = true;
+        # Disable pam_mount in systemd-user to prevent it from being called
+        # multiple times during login, because it will prevent pam_mount from
+        # unmounting the previously mounted volumes.
+        pamMount = false;
       };
 
     # Some overrides to upstream units.