Add the tempest cloud test suite to an image.

The purpose of this element is to run tempest as a gate for tripleo based ci.

To successfully run tempest your overcloud should have
 o Nodes with at least 4G of memory and 20G of diskspace
 o the following services should be running
   cinder, glance, heat, keystone, neutron, nova and swift

To use you should simply run the command run-tempest with the
OS_* environment variables for admin defined.

TODO:
 o Remove as many of the filters in tests2skip.txt as possible
 o Investigate setting allow_tenant_isolation to true
 o Investigate setting run_ssh to true
