openstack-ironic-inspector-dnsmasq.service fails to start after undercloud reboot

Issue

• Failed to start PXE boot dnsmasq service for Ironic Inspector.

• After installing the Undercloud, and rebooting, the openstack-ironic-inspector-dnsmasq.service unit fails to start:

stack@ESJC-OST3-UC01P:~$ sudo systemctl status openstack-ironic-inspector-dnsmasq.service -l
● openstack-ironic-inspector-dnsmasq.service - PXE boot dnsmasq service for Ironic Inspector
   Loaded: loaded (/usr/lib/systemd/system/openstack-ironic-inspector-dnsmasq.service; enabled; vendor preset: disabled)   Active: failed (Result: exit-code) since Tue 2017-08-01 16:14:56 CEST; 1min 7s ago
  Process: 940 ExecStart=/sbin/dnsmasq --conf-file=/etc/ironic-inspector/dnsmasq.conf (code=exited, status=2)

Aug 01 16:14:56  systemd[1]: Starting PXE boot dnsmasq service for Ironic Inspector...
Aug 01 16:14:56  dnsmasq[940]: dnsmasq: unknown interface br-ctlplane
Aug 01 16:14:56systemd[1]: openstack-ironic-inspector-dnsmasq.service: control process exited, code=exited status=2
Aug 01 16:14:56  systemd[1]: Failed to start PXE boot dnsmasq service for Ironic Inspector.
Aug 01 16:14:56 systemd[1]: Unit openstack-ironic-inspector-dnsmasq.service entered failed state.
Aug 01 16:14:56 systemd[1]: openstack-ironic-inspector-dnsmasq.service failed.