Add X-Frame-Options and frame-ancestors options

These two options allow preventing clickjacking attacks. They don't allow
open FreeIPA in frame, iframe or object element.

https://fedorahosted.org/freeipa/ticket/4631

Reviewed-By: Petr Vobornik <pvoborni@redhat.com>
Reviewed-By: Simo Sorce <ssorce@redhat.com>

install/conf/ipa.conf

@@ -1,5 +1,5 @@
 #
-# VERSION 19 - DO NOT REMOVE THIS LINE
+# VERSION 20 - DO NOT REMOVE THIS LINE
 #
 # This file may be overwritten on upgrades.
 #
@@ -71,6 +71,8 @@ WSGIScriptReloading Off
   ErrorDocument 401 /ipa/errors/unauthorized.html
   WSGIProcessGroup ipa
   WSGIApplicationGroup ipa
+  Header always append X-Frame-Options DENY
+  Header always append Content-Security-Policy "frame-ancestors 'none'"
 </Location>
 
 # Turn off Apache authentication for sessions