Switch DEVSTACK_SERIES to queens
Switch DEVSTACK_SERIES to queens

pike is handled in stable/pike branch for some time
already.

Change-Id: I47dc5bf661c50b3b05c19ad665c2671f807233ae

openstack-dev/devstack,group-policy/devstack,nawawi/openstack,group-policy/devstack,noironetworks/devstack,dtroyer/devstack,openstack-dev/devstack,dtroyer/devstack,nawawi/openstack,noironetworks/devstack