Do not overwrite nosetests exit code with tee

When output of nosetests is piped to tee, tee's exit status overwrites
that of nosetests, and the pipeline returns 0 even on failures and
errors.

This reverts part of the changes done in:
440aded2f5025a8117bf87f74de8c24ef79f68a5

Change-Id: I37db61be9c9dae105324319f995a7d65a9907531
Closes-bug: #1300483
Signed-off-by: Dmitry Borodaenko <dborodaenko@mirantis.com>
Merge "Do not overwrite nosetests exit code with tee" into stable/4.1