t/lib-httpd: pass LANG and LC_ALL to Apache

t/lib-httpd: pass LANG and LC_ALL to Apache

t5411 starts a web server with no explicit language setting, so it uses
the system default.  Ten of its tests expect it to return error messages
containing the prefix "fatal: ", emitted by die().  This prefix can be
localized since a1fd2cf8cd (i18n: mark message helpers prefix for
translation, 2022-06-21), however.  As a result these ten tests break
for me on a system with LANG="de_DE.UTF-8" because the web server sends
localized messages with "Schwerwiegend: " instead of "fatal: ".

Fix these tests by passing LANG and LC_ALL to the web server, which are
set to "C" by t/test-lib.sh, to get untranslated messages on both sides.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>