Fix metadata service not reachable from instance

The warning message like below
checking http://169.254.169.254/2009-04-04/instance-id
failed 1/20: up 7.41. request failed
failed 2/20: up 9.95. request failed
failed 3/20: up 12.33. request failed
failed 4/20: up 14.73. request failed
failed 5/20: up 17.15. request failed

It will also cause Network node crash if Ubuntu instance is launched

Reference: https://ask.openstack.org/en/question/27505/metadata-problem-in-neutron-flat-network/