Comment 3 for bug 1493228

I checked live environment and confirm that dhcp_agent for 'net04' network are running only on 2 controllers, because dhcp_agents_per_network parameter is set to 2:

https://github.com/stackforge/fuel-library/blob/master/deployment/puppet/openstack/manifests/network.pp#L182
https://github.com/stackforge/fuel-library/commit/89ef0dadcbb8bf7b4b9ec36110f0a97848f99eff

So looks like the tests which try to ping/access instances using DHCP agent net namespace from random controller should be fixed: list of nodes with running agents for specific network must be fetched from neutron:

root@node-4:~# neutron agent-list | grep DHCP
| 1b233ec4-dbdf-4bfb-bbfd-79737df1210d | DHCP agent | node-6.test.domain.local | :-) | True | neutron-dhcp-agent |
| 5394460f-0cb3-4f53-af3c-f3ea26bf21c0 | DHCP agent | node-5.test.domain.local | :-) | True | neutron-dhcp-agent |
| e5d21dd2-6549-4289-be14-aa20bd631199 | DHCP agent | node-4.test.domain.local | :-) | True | neutron-dhcp-agent |

root@node-4:~# neutron dhcp-agent-list-hosting-net net04
+--------------------------------------+--------------------------+----------------+-------+
| id | host | admin_state_up | alive |
+--------------------------------------+--------------------------+----------------+-------+
| 1b233ec4-dbdf-4bfb-bbfd-79737df1210d | node-6.test.domain.local | True | :-) |
| 5394460f-0cb3-4f53-af3c-f3ea26bf21c0 | node-5.test.domain.local | True | :-) |
+--------------------------------------+--------------------------+----------------+-------+