Fix serving of gerrit repos with '/p' in url

This change is similiar to I70d814a5eae
By default /p is served by gerrit itself so the normal proxying to
gerrit makes /p work. However for us we want /p to bypass gerrit
and hit the local git repo replica which requires running a git cgi
script so apache needs to be told that it is ok to do that.

It was giving the following error:
'fatal: unable to access 'https://review-dev.openstack.org/p/gtest-org/test2/':
The requested URL returned error: 403'

Change-Id: Iffdcefb2215a468fce3836d46377f4d1344e73b9

manifests/init.pp

@@ -358,6 +358,11 @@ class gerrit(
   a2mod { 'proxy_http':
     ensure => present,
   }
+  if ! defined(A2mod['cgi']) {
+    a2mod { 'cgi':
+      ensure => present,
+    }
+  }
 
   if $ssl_cert_file_contents != '' {
     file { $ssl_cert_file:

templates/gerrit.vhost.erb

@@ -83,7 +83,10 @@
     Order allow,deny
     Allow from all
   </Directory>
-
+  <Directory /usr/lib/git-core>
+    Allow from all
+    Satisfy Any
+  </Directory>
 
 </VirtualHost>
 </IfModule>