Network does not come up after the OS install during overcloud scaleout or deployment

Issue

• Whenever we are scaling/adding more computes with overcloud deployment, the node gets installed and the network does not come up. We have to stop the overcloud, reboot the baremetal nodes using nova commands and then restart the overcloud scale out.

• os-collect-config returns an error similar to this:

Nov 14 12:18:09 overcloud-compute-0 os-collect-config: [2019/11/14 12:17:13 PM] [INFO] Running ip route add 169.254.169.254/32 via 10.10.10.10 dev br-ex
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: [2019/11/14 12:17:13 PM] [WARNING] Error in 'ip route add 169.254.169.254/32 via 10.10.10.10 dev br-ex', restarting br-ex:
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: Unexpected error while running command.
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: Command: /sbin/ip route add 169.254.169.254/32 via 10.10.10.10 dev br-ex
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: Exit code: 1
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: Stdout: u''
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: Stderr: u'Cannot find device "br-ex"\n'
...
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: + echo -n 'Trying to ping metadata IP 10.10.10.10...'
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: + _ping=ping
...
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: + echo '10.10.10.10 is not pingable.'
Nov 14 12:18:09 overcloud-compute-0 os-collect-config: 10.10.10.10 is not pingable.