Don't set constrained delegation

Not supported in Ubuntu trusty
diff --git a/apache/files/_auth.conf b/apache/files/_auth.conf
index d64de96..c7b6315 100644
--- a/apache/files/_auth.conf
+++ b/apache/files/_auth.conf
@@ -18,7 +18,7 @@
   KrbAuthRealms {{ site.auth.kerberos.realms|join(' ') }}
   Krb5KeyTab {{ site.auth.kerberos.get("keytab", "/etc/apache2/ipa.keytab") }}
   KrbSaveCredentials on
-  KrbConstrainedDelegation on
+  #KrbConstrainedDelegation on
 
   # Ensure X-Forwarded-User is correctly set
   RequestHeader unset X-Forwarded-User