The most important issue is that after unsetting `i18n.commitencoding'
config variable t9500 no longer will use author and comitter name
containing ISO-8859-1 characters, which are invalid UTF-8 characters.
Besides it is good practice in general to clean up the state in tests.
Signed-off-by: Jakub Narebski <jnareb@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>