Switch to using testr as the test runner for everything non-gating.

This commit switches the test runner in tempest to testr from nose for all
jobs that aren't gating. This will allow the usage of parallel testing with
the use of a group_regex in testr. Group_regex will ensure that the classes
get scheduled together and the run times are tracked together. Than the
tools/run_test_classes.py script will filter the test_ids and pass only the
classes to subunit.run to ensure we are only running setupClass once.

This commit also adds a new option to run_tests.sh. -t/--with-testr can be
used to optionally run tempest in parallel with testr. Once running with
testr gets stable enough this will become the default for run_tests.

It also adds a testr-full tox job so we can have a tracking non-voting job
that runs the same tests as the gate but with testr.

Implements: blueprint speed-up-tempest

Change-Id: Iedc9bd92b8f8471c60c614c7d7c05046d7b32743
Fix stress-tox-job.json action file.

Change I39b8a1d38f70ddda4867126b58bb7053b45654d6 changed how the
actions are called, but stress-tox-job.json was merged at the same
time. This commit updates the json definition to use the new paths
so that the tox job will work again.

Part of: blueprint stress-tests

Change-Id: Idadf08e0cc3f01650e72ca078a223781a0f1669a
Merge "Switch to using testr as the test runner for everything non-gating."