this should fix the failing gate

This reverts the oslo.util pin we had now that its in our requirments.txt
and also avoids pymonogo 3.1 causing seg faults.

Change-Id: I4f4daf7a458520799bfbf4368851434c67029324
Closes-Bug: #1512870

tox.ini

@@ -9,7 +9,7 @@ usedevelop = True
 install_command = pip install -U {opts} {packages}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = pip install oslo.utils===2.5.0
+commands = pip install pymongo===3.0.3
            {envpython} run_tests.py
            python setup.py testr --slowest
            {envpython} generate_examples.py