Add missing global options in dnsconfig

Add a support for new global options in bind-dyndb-ldap, that is:
 * idnsforwardpolicy: Default policy for conditional forwarding
 * idnsallowsyncptr: Allow globaly PTR synchronization for dynamic
   updates
 * idnszonerefresh: Default interval between regular polls of the
   name server for new DNS zones

https://fedorahosted.org/freeipa/ticket/2439

ipalib/plugins/dns.py

@@ -2640,7 +2640,10 @@ class dnsconfig(LDAPObject):
     DNS global configuration object
     """
     object_name = _('DNS configuration options')
-    default_attributes = [ 'idnsforwarders', ]
+    default_attributes = [
+        'idnsforwardpolicy', 'idnsforwarders', 'idnsallowsyncptr',
+        'idnszonerefresh'
+    ]
 
     label = _('DNS Global Configuration')
     label_singular = _('DNS Global Configuration')
@@ -2654,6 +2657,22 @@ class dnsconfig(LDAPObject):
                   'for each forwarder using a standard format "IP_ADDRESS port PORT"'),
             csv=True,
         ),
+        StrEnum('idnsforwardpolicy?',
+            cli_name='forward_policy',
+            label=_('Forward policy'),
+            values=(u'only', u'first',),
+        ),
+        Bool('idnsallowsyncptr?',
+            cli_name='allow_sync_ptr',
+            label=_('Allow PTR sync'),
+            doc=_('Allow synchronization of forward (A, AAAA) and reverse (PTR) records'),
+        ),
+        Int('idnszonerefresh?',
+            cli_name='zone_refresh',
+            label=_('Zone refresh interval'),
+            doc=_('An interval between regular polls of the name server for new DNS zones'),
+            minvalue=0,
+        ),
     )
 
     def get_dn(self, *keys, **kwargs):