Avoid apache complaining about lack of server's FQDN

On some setups, apache will say:
apache2: Could not reliably determine the server's fully qualified
domain name, using $(IP_address) for ServerName

Avoid this message polluting tests output by setting a ServerName in
apache configuration.

Signed-off-by: Mike Hommey <mh@glandium.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-httpd/apache.conf

@@ -1,3 +1,4 @@
+ServerName dummy
 PidFile httpd.pid
 DocumentRoot www
 ErrorLog error.log