Update coord attrs in _update_metadata_increased_resolution()

The coordinates of a DataArray that has been interpolated will have
attrs that are not consistent with the new DataArray. This commit
updates _update_metadata_increased_resolution() to also replace the
attrs of the DataArray's coords with the attrs of the new DataArray.

xbout/utils.py

@@ -87,4 +87,9 @@ def update_ny(name):
     update_ny('ny_inner')
     update_ny('MYSUB')
 
+    # Update attrs of coordinates to be consistent with da
+    for coord in da.coords:
+        da[coord].attrs = {}
+        _add_attrs_to_var(da, coord)
+
     return da