Limit psutil to <2.0.0

The psutil package recently released psutil version 2.0.0.  This version
made a significant number of changes that are not backwards-compatible.
We should thus restrict the OpenStack psutil requirement to <2.0.0 until
we can ensure that our code is compatible with the new API and that the
2.0.0 version of psutil has had time to propogate to the various
distros.

Needed by: https://review.openstack.org/#/c/78793/
Change-Id: I63d01235a949cd10ba87d41ad428818daaf9a756
Work around atexit bug in python < 2.7.4

In python < 2.7.4, a lazy loading of package `pbr` will break
setuptools if some other modules registered functions in `atexit`.
solution from: http://bugs.python.org/issue15881#msg170215

This problem originally appeared in stevedore
before the library was adopted by Oslo
(https://github.com/dreamhost/stevedore/commit/74a719b11781cc93d60cff1b0a01de3e4e780a1d)

This change places the fix from Icd412ca8435dca4b0f3b4075eca39b903dde6d27
in the right location to be synced into the other repositories.

Change-Id: I7560e474e68bf361f3af61bdfc8e2dbc9e2413f1
Merge "Work around atexit bug in python < 2.7.4"
Merge "Limit psutil to <2.0.0"