Move ironic default test node to trusty.
Move ironic default test node to trusty.

This change will run all ironic and ironic specs python27
unittests, doc builds, and flake8 jobs on trusty nodes.

Change-Id: I0d3726b052b4374f386bbb39b9ce44cf4eea68af

citrix-openstack/project-config,Tesora/tesora-project-config,osrg/project-config,coolsvap/project-config,open-switch/infra_project-config,openstack-infra/project-config,noorul/os-project-config,anbangr/osci-project-config,noorul/os-project-config,citrix-openstack/project-config,openstack-infra/project-config,anbangr/osci-project-config,Tesora/tesora-project-config,coolsvap/project-config,open-switch/infra_project-config,dongwenjuan/project-config,dongwenjuan/project-config,osrg/project-config