Ticket #47960 - cookie_change_info returns random negative number if there was no change in a tree
    
    Description: When no changes had not been made, Retro Changelog db
    was empty and the search callback sync_handle_cnum_entry in the
    Content Synchronization had no chance to be called.  If it was not
    called, an uninitialized garbage value in Sync_CallBackData was set
    to cookie_change_info.
    
    This patch checks if the search callback sync_handle_cnum_entry is
    called or not.  If it is not called, set 0 to cookie_change_info.
    
    https://fedorahosted.org/389/ticket/47960
    
    Reviewed by rmeggins@redhat.com and tbordaz@redhat.com (Thank you,
    Rich and Thierry!!)
    
    (cherry picked from commit a908c6b57cd77ff2f6e2fe0fe1fa2e0eccba77e0)