Fix psutil.cpu_times unpack error

[dongweiming]

What does this PR do?

I got a error when use sudo salt '*' ps.top:

130:
    The minion function caused an exception: Traceback (most recent call last):
      File "/usr/lib/python2.7/dist-packages/salt/minion.py", line 1071, in _thread_return
        return_data = func(*args, **kwargs)
      File "/usr/lib/python2.7/dist-packages/salt/modules/ps.py", line 136, in top
        user, system = process.cpu_times()
    ValueError: too many values to unpack

We need compatible with the new method.

What issues does this PR fix or reference?

giampaolo/psutil#785 Now cpu_times return four values

New Behavior

Now ps.top works.

Tests written?

No

[cachedout]

Nice! Thanks, @dongweiming