tempest: Log server console output of failed SSH
tempest: Log server console output of failed SSH

Tempest has a code in its base class. As we inherit from API base class
in tempest tests, we lost this capability. This patch adds a copy from
tempest code.

Change-Id: I24fc7e4c5f2726a16af15288987e65b77532e709

huntxu/neutron,openstack/neutron,noironetworks/neutron,openstack/neutron,mahak/neutron,eayunstack/neutron,mahak/neutron,eayunstack/neutron,noironetworks/neutron,openstack/neutron,mahak/neutron,huntxu/neutron