Add unit tests for benchmark scenarios

Added following unit tests

1. Ceilometer
test_create_and_query_alarms_no_filter
test_create_and_query_samples_no_filter
2. Dummy
t_dummy_dummy_with_scenario_output
3. Heat
test_heat_resource_is

Change-Id: I21a877a0b4d63febf3043fc7445d3bb051374093
Implements: blueprint improve-unit-test-coverage-rally
Merge "Add unit tests for benchmark scenarios"