LP#1641208: util.file no longer mangles UTF8 when writing JSON

LP#1641208: util.file no longer mangles UTF8 when writing JSON

This patch ensures that JSON strings are converted to UTF8
before they are writing to XUL profile files by util.file. Doing this
fixes a bug where by OU names like "ბიზნესისა" can get mangled
in certain XUL client interfaces.

To test
-------
[1] Set an OU name to ბიზნესისა
[2] In the transit list, note that the OU selector displays
    the name as ÑØÖÜÔáØáÐ.
[3] Apply the patch (note that it's not necessary to rebuild
    the staff client to test this).
[4] Restart the staff client, clearing cache beforehand.
[5] Note that the OU name is now displayed correctly in the transit
    list.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>