import: wire up SYSTEMD_IMPORT_BTRFS_{SUBVOL,QUOTA} to importd

Btrfs quotas are actually being enabled in systemd-importd via
setup_machine_directory(), not in systemd-{import,pull} where those
environment variables are checked. Therefore, also check them in
systemd-importd and avoid enabling quotas if requested by the user.

Fixes: #18421
Fixes: #15903
Fixes: #24387

src/machine/machined-dbus.c

@@ -863,7 +863,7 @@ static int method_set_pool_limit(sd_bus_message *message, void *userdata, sd_bus
                 return 1; /* Will call us back */
 
         /* Set up the machine directory if necessary */
-        r = setup_machine_directory(error);
+        r = setup_machine_directory(error, /* use_btrfs_subvol= */ true, /* use_btrfs_quota= */ true);
         if (r < 0)
                 return r;