Wrong minzoom exposed as metadata if write_to is used #935

{
    "layers": {
        "streets": {
            "minzoom": 14,
            "maxzoom": 14,
            "combine_below": 15
        },
        "streets_med": {
            "minzoom": 11,
            "maxzoom": 13,
            "simplify_below": 14,
            "simplify_level": 0.0002,
            "combine_below": 14,
            "write_to": "streets"
        },
        "streets_low": {
            "minzoom": 5,
            "maxzoom": 10,
            "simplify_below": 14,
            "simplify_level": 0.0001,
            "combine_below": 11,
            "write_to": "streets"
        }
    },
    "settings": {
        "minzoom": 0,
        "maxzoom": 14,
        "basezoom": 14,
        "include_ids": false,
        "combine_below": 14,
        "name": "Shortbread",
        "version": "1.0",
        "description": "Tile config for a simple vector tiles schema",
        "compress": "gzip",
        "filemetadata": {
            "tilejson": "2.0.0",
            "scheme": "xyz",
            "type": "baselayer",
            "format": "pbf",
            "tiles": [
                "https://example.com/liechtenstein/{z}/{x}/{y}.pbf"
            ]
        },
        "metadata": {
          "author": "OpenStreetMap contributors, Geofabrik GmbH",
          "license": "Open Database License 1.0"
        }
    }
}