Changed the log format for horizon's apache configuration

The default apache log format is noisy. Added a custom log format
that matches the other apache log format of projects like keystone

Closes-Bug: #1222900
Change-Id: Id9a8c3a4413c778e009c56ffde6b646b8a120c8b
diff --git a/files/apache-horizon.template b/files/apache-horizon.template
index bca1251..6883898 100644
--- a/files/apache-horizon.template
+++ b/files/apache-horizon.template
@@ -28,7 +28,9 @@
             Require all granted
         </IfVersion>
     </Directory>
-
+    <IfVersion >= 2.4>
+      ErrorLogFormat "%{cu}t %M"
+    </IfVersion>
     ErrorLog /var/log/%APACHE_NAME%/horizon_error.log
     LogLevel warn
     CustomLog /var/log/%APACHE_NAME%/horizon_access.log combined