Get csrf token properly when retry bodhi API call
    
    self.csrf must be called before trying to call method to save and extend
    Bodhi update. This patch fixes two issues, 1) incorrect call to cookies
    clear method, 2) call self.csrf to get a new token before second call of
    send_request to extend update expiration.
    
    For simplicity, retry is refactored into a decorator.
    
    Signed-off-by: Chenxiong Qi <cqi@redhat.com>