Comment # 2 on bug 954329 from Lars Marowsky-Bree

(In reply to Pawel Wieczorkiewicz from comment #1)
> Have you had br0(enp0s25) running before? 

Yes, I had that configuration in the past. (And then figured out that that
didn't work as I needed it to, and removed the enslaved device from the
configuration.)

> If so have you ifdown all (or ifdown br0 _and_ ifdown enp0s25) the interface
> before ifup br0 with new config?

Yes. I restarted both all network interfaces, and wickedd.

Karol eventually suggested I try:

# rm /var/run/wicked/state-*

which made the problem go away, and it's now behaving as expected. I didn't
save the state-* files for debugging though :-(