Add log_format variable for apache openstack sites

Add openstack default variables with log formats for apache sites

Aligh log settings with settings from formulas for openstack
services: aodh, barbican, cinder, gnocchi, manila, nova-placement,
panko.

Change-Id: Ie59d341c39e9c50292f4fe28c6227766961d250c
PROD-Related: PROD-28066 (PROD:28066)
diff --git a/apache/server/site/manila.yml b/apache/server/site/manila.yml
index 3080d1d..163f237 100644
--- a/apache/server/site/manila.yml
+++ b/apache/server/site/manila.yml
@@ -38,8 +38,8 @@
             port: 8786
           log:
             custom:
-              format: >-
-                %v:%p %{X-Forwarded-For}i %h %l %u %t \"%r\" %>s %D %O \"%{Referer}i\" \"%{User-Agent}i\"
+              format: ${_param:apache_site_openstack_manila_log_format}
+              file: /var/log/apache2/manila.access.log
             error:
               enabled: true
               level: debug