Bridge does not get IP via DHCP at boot

I'm running CentOS 7. I'm not running NetworkManager, and I've actually uninstalled it.

My system is supposed to acquire an IPv4 address via DHCP on br0 at boot. Howver, when I log in, it has no address.

My configuration:

# pwd
/etc/sysconfig/network-scripts

# cat ifcfg-enp5s0 
DEVICE=enp5s0
ONBOOT="yes"
BRIDGE=br0

# cat ifcfg-br0 
DEVICE=br0
ONBOOT=yes
TYPE=Bridge
BOOTPROTO=dhcp
STP=on
DELAY=0

Note that I didn't configure this bridge manually; virt-manager did so when I added br0 on this dialog:

Looking through journalctl --boot, I see:

Jan 08 21:04:34 jonathon-centos7 kernel: r8169 0000:05:00.0 enp5s0: link up
Jan 08 21:04:34 jonathon-centos7 kernel: IPv6: ADDRCONF(NETDEV_CHANGE): enp5s0: link becomes ready
Jan 08 21:04:34 jonathon-centos7 kernel: br0: port 1(enp5s0) entered listening state
Jan 08 21:04:34 jonathon-centos7 kernel: br0: port 1(enp5s0) entered listening state
Jan 08 21:04:36 jonathon-centos7 avahi-daemon[957]: Registering new address record for fe80::f66d:4ff:fe3b:c24e on enp5s0.*.
Jan 08 21:04:36 jonathon-centos7 kernel: br0: port 1(enp5s0) entered learning state
Jan 08 21:04:38 jonathon-centos7 network[947]: Determining IP information for br0... failed; no link present.  Check cable?
Jan 08 21:04:38 jonathon-centos7 network[947]: [FAILED]
Jan 08 21:04:38 jonathon-centos7 systemd[1]: network.service: control process exited, code=exited status=1
Jan 08 21:04:38 jonathon-centos7 systemd[1]: Failed to start LSB: Bring up/down networking.

After the system boots, and I'm logged-in, I can open a terminal, and:

# ifup br0
set forward delay failed: Numerical result out of range

Determining IP information for br0... done.

And then I'm connected to my network.

Why am I unable to get an IP for br0 at boot?

Related:

• Ethernet bridge with dhcp [CentOS forms]