In contrast to apache 2.2, apache 2.4 does not load mod_unixd in its
default configuration (because there are choices). Thus, with the
current config, apache 2.4.10 will not be started and the httpd tests
will not run on distros with default apache config (RedHat type).

Enable mod_unixd to make the httpd tests run. This does not affect
distros negatively which have that config already in their default
(Debian type). httpd tests will run on these before and after this patch.
Signed-off-by: NMichael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>