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/barbican.yml b/apache/server/site/barbican.yml
index 0e7da2c..7a4297b 100644
--- a/apache/server/site/barbican.yml
+++ b/apache/server/site/barbican.yml
@@ -31,7 +31,7 @@
             port: 9311
           log:
             custom:
-              format: 'combined'
+              format: ${_param:apache_site_openstack_barbican_log_format}
               file: '/var/log/barbican/barbican-api.log'
             error:
               enabled: true
@@ -55,7 +55,7 @@
             port: 9312
           log:
             custom:
-              format: 'combined'
+              format: ${_param:apache_site_openstack_barbican_log_format}
               file: '/var/log/barbican/barbican-api.log'
             error:
               enabled: true