Fix the 4 broken tests in fuel-web

Fix broken change in test_task_handler so that right parent class is
 used

Fix test_cluster_changes_handler to include pg_num

Change-Id: I6c9630195981626fceb1f763a9c010cfb8008b32
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: Ia7fc2ab5719c878c740d9167d31cdaa018404c3c
Closes-bug: #1300483
Signed-off-by: Dmitry Borodaenko <dborodaenko@mirantis.com>