def http_delete(opts={})
      ret=http_delete_low(opts)
      if ret.is_a?(Hash) and ret.has_key?('error') and ret['error']=='Invalid Credentials' then
	authdefault
	ret=http_delete_low(opts)
	return ret
      else
	return ret
      end
    end
def http_delete(opts={})
      ret=http_delete_low(opts)
      if ret.is_a?(Hash) and ret.has_key?('error') and ret['error']=='Invalid Credentials' then
	authdefault
	ret=http_delete_low(opts)
	return ret
      else
	return ret
      end
    end
Perform HTTP delete method with uri, data and fields

 returns: HTTP result object

 Usage:

  n=NessusREST::Client.new (:url=>'https://localhost:8834', :username=>'user', :password=> 'password')
  res = n.http_delete(:uri=>"/session", :fields=>n.x_cookie)
  puts res.code