Move novaclient default test node to trusty.
Move novaclient default test node to trusty.

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

Change-Id: Iacc7258444d2f9a64db33869c9063a25b75b07ec

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