Change logging in stress test

Stress tests is now using the default tempest logging in order to use
tempest.conf for configuration. Every action registers a logger for
their own (previously they reported always as "stresstest").

Cleanup function is adapted as well.

Implements: bp stress-tests

Change-Id: I571d4b1ad7ced62b5d5b3e7faf8fa1a7e5f9504e
Merge "Change logging in stress test"