Add tempest unit test cases

Added missing tempest test cases
as part of unit test coverage.

test_single_test_negative
test_set_smoke
test_set_full
test_set_from_list
test_set_selective
test_specific_regex

Change-Id: I89d96ce4142dd72c79fdd21b100addd56ae03188
Implements: blueprint improve-unit-test-coverage-rally
Merge "Add tempest unit test cases"