Use the apache 2.4 ErrorLogFormat directive

Use the new ErrorLogFormat directive to make the Keystone logs
under Apache to look like the standard oslo log format.

Change-Id: Ie823abf2fa06b8ce22027c21bef455808a4a768e
diff --git a/files/apache-keystone.template b/files/apache-keystone.template
index a9d9cc3..e7b2157 100644
--- a/files/apache-keystone.template
+++ b/files/apache-keystone.template
@@ -6,6 +6,7 @@
     WSGIProcessGroup keystone-public
     WSGIScriptAlias / %PUBLICWSGI%
     WSGIApplicationGroup %{GLOBAL}
+    %ERRORLOGFORMAT%
     ErrorLog /var/log/%APACHE_NAME%/keystone.log
     CustomLog /var/log/%APACHE_NAME%/access.log combined
 </VirtualHost>
@@ -15,6 +16,7 @@
     WSGIProcessGroup keystone-admin
     WSGIScriptAlias / %ADMINWSGI%
     WSGIApplicationGroup %{GLOBAL}
+    %ERRORLOGFORMAT%
     ErrorLog /var/log/%APACHE_NAME%/keystone.log
     CustomLog /var/log/%APACHE_NAME%/access.log combined
 </VirtualHost>