Switching to oslo importutils in the stress tests

The importutils is helper module for dynamic class and module,
 loading.

The importutils is compatible with python 2.6 and it is
used in multiple other openstack projects.

The previously used importlib defined with python 2.7.

Change-Id: I4e99ccf9d51cea28584c9d28a4aceab633b3f998
2 files changed