Since it's not really used and a bit complex. It was only used
for negative compute flavor tests, and I think we can live easily
without these tests.
This commit adds omit files for coverage. In tempest, we can get
coverage of its unit tests. But we don't need the coverage of api tests,
scenario tests and api_schema. Because we don't need to have their unit
We don't need the result of tempest/tests/* and tempest/openstack/*
coverage. This commit omits it with introducing .coveragerc.
Partially implements bp unit-tests