Move test_server_cfn_init from tempest to heat

The only changes required to move this test have been:
* Change the imports
* Use the DEFAULT CONF group for conf options

Change-Id: Ic9474e329b9cef1e96b693f10c320b612f580283
Partial-Blueprint: functional-tests
Merge "Move test_server_cfn_init from tempest to heat"