Adding missing test cases of "test_verify_tempest_config"

Some of test cases are missing from "test_verify_tempest_config"
This patch will add them.
It will cover both positive and negative unit tests.

Change-Id: I0c929749039ec8d30dc801a1d3d0f53e3415a102
Partially-Implements: blueprint tempest-cli-unit-test-coverage
1 file changed