tests: use pytest parametrization for test_guess.py
tests: use pytest parametrization for test_guess.py

Use pytest's paramterize method to run individual tests for each test
case.

This makes the output of "pytest -v" clearer. It makes it easier to
see the exact test that failed. This also causes pytest to run all the
tests, rather than bailing out after the first AssertionError.

Change-Id: If42a8c89c6f7bb2c4a1e8311bbb4e75197b13d31

openstack-packages/rdopkg,openstack-packages/rdopkg,redhat-openstack/rdopkg,redhat-openstack/rdopkg