Comment 4 for bug 1155092

Further analysis shows that it's possible to delete namespace after another namespace is used to restart haproxy.
At first glance those events seem unrelated, however issue is reproducible nearly at 100% cases with the following steps:
1)Create pool1
2)Create pool2
3)Create vip1 (for pool1)
3)Create vip2 (for pool2)
3)Delete vip1
Fails with "Device or resource busy"
The namespace could not be removed manually as well.

That causes state resync and restart of haproxy in the namespace of VIP2
After that, namespace of vip1/pool1 can be deleted manually.

That seems like some bug in netns support.