Add two system tests for Heat

Now there is only one system test that run OSTF Heat tests on simple cluster with
Neutron GRE.
Test that run tests on simple cluster with Nova network and test that run test
on cluster with HA mode were added. We need to run OSTF tests in different network
configuration because Heat use different templates for them.

Implements blueprint: add-more-heat-system-tests

Change-Id: Id41401be81f198037044b76f6bf9ff0a5e023c67
Merge "Add two system tests for Heat"