zabbix::web: Allow httpd to speak to the database

Turns out our acceptance tests fail in vagrant because the default
centos image has selinux enabled. The docker image on travis not. The is
an selinux boolean to allow the httpd service to speak to a database. By
default this is of. This PR fixes this.

Author: bastelfreak

manifests/web.pp

@@ -468,9 +468,15 @@
 
   # check if selinux is active and allow zabbix
   if fact('os.selinux.enabled') == true and $manage_selinux {
+    # allow httpd to speak to the zabbix service
     selboolean{'httpd_can_connect_zabbix':
       persistent => true,
       value      => 'on',
     }
+    # allow httpd to speak to the database
+    selboolean{'httpd_can_network_connect_db':
+      persistent => true,
+      value      => 'on',
+    }
   }
 }