t/lib-httpd/apache.conf: do not use LockFile in apache >= 2.4

The LockFile directive from earlier versions of apache has
been replaced by the Mutex directive. The latter seems to
give sane defaults and does not need any specific
customization, so we can get away with just adding a version
check to the use of LockFile.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-httpd/apache.conf

@@ -1,5 +1,7 @@
 ServerName dummy
+<IfVersion < 2.4>
 LockFile accept.lock
+</IfVersion>
 PidFile httpd.pid
 DocumentRoot www
 LogFormat "%h %l %u %t \"%r\" %>s %b" common