Reset state unit tests failures

Depending on the order in which reset status tests are executed we could get failures, which means that we have either tests that mess the system or tests that depend on other tests.

I have narrowed it down quite a bit. If we run "cinderclient.tests.unit.v3.test_shell.ShellTest.test_attachment_create_*" first and then "cinderclient.tests.unit.v3.test_shell.ShellTest.test_reset_state_volume_additional_status_*" we'll get following error:

stdout: {{{'ShellTest' object has no attribute 'reset_state'}}}

Traceback (most recent call last):
  File "/home/geguileo/code/stack/python-cinderclient/.tox/py35/lib/python3.5/site-packages/ddt.py", line 139, in wrapper
    return func(self, *args, **kwargs)
  File "/home/geguileo/code/stack/python-cinderclient/.tox/py35/lib/python3.5/site-packages/mock/mock.py", line 1305, in patched
    return func(*args, **keywargs)
  File "/home/geguileo/code/stack/python-cinderclient/cinderclient/tests/unit/v3/test_shell.py", line 699, in test_reset_state_volume_additional_status
    self.run_command('reset-state %s 1234' % command)
  File "/home/geguileo/code/stack/python-cinderclient/cinderclient/tests/unit/v3/test_shell.py", line 66, in run_command
    self.shell.main(cmd.split())
  File "/home/geguileo/code/stack/python-cinderclient/cinderclient/shell.py", line 785, in main
    args.func(self.cs, args)
  File "/home/geguileo/code/stack/python-cinderclient/cinderclient/v3/shell.py", line 412, in do_reset_state
    raise exceptions.CommandError(msg)
cinderclient.exceptions.CommandError: Unable to reset the state for the specified entity(s).