the *_ssh drivers in ironic are unsupported since Newton and slated for
removal in Pike.
This patch moves gate-mogan-dsvm-tempest-plugin job to set up ironic
with agent_ipmitool driver insead of agent_ssh one.
This change was tested [0] with force-enabled *_ipmitool drivers and
the job in question has succeeded.
[0] https://review.openstack.org/#/c/452720
Change-Id: I06b72cb07cac0c864ad1713d0379e5496bdc1919
Related-Bug: #1570301