Add API for PTR sync control
    
    New version of bind-dyndb-ldap plugin have an ability to
    automatically update machine reverse address when its forward
    address is updated via GSS-TSIG update. The reverse zone must be
    managed by FreeIPA as well in order of this feature to work.
    
    As it would not be secure to enable this behaviour for all zones
    there is a global attribute that can enable PTR sync for all zones
    and also a per-zone attribute that can enable for chosen zones
    only.
    
    This patch adds an API for this control.
    
    https://fedorahosted.org/freeipa/ticket/2176