Import context from neutron_lib

[Sridhar Venkat]

Changes in https://review.openstack.org/#/c/442540/ need to be backported to stable/ocata.

Otherwise, the following exceptions occur:
2017-03-09 20:15:32.556738 | Traceback (most recent call last):
2017-03-09 20:15:32.556797 | File "/home/jenkins/workspace/gate-networking-powervm-python27-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/unittest2/loader.py", line 456, in _find_test_path
2017-03-09 20:15:32.556823 | module = self._get_module_from_name(name)
2017-03-09 20:15:32.556884 | File "/home/jenkins/workspace/gate-networking-powervm-python27-ubuntu-xenial/.tox/py27/local/lib/python2.7/site-packages/unittest2/loader.py", line 395, in _get_module_from_name
2017-03-09 20:15:32.556906 | __import__(name)
2017-03-09 20:15:32.556946 | File "networking_powervm/tests/unit/plugins/ibm/powervm/test_agent_base.py", line 23, in <module>
2017-03-09 20:15:32.556978 | from networking_powervm.plugins.ibm.agent.powervm import agent_base
2017-03-09 20:15:32.557013 | File "networking_powervm/plugins/ibm/agent/powervm/agent_base.py", line 28, in <module>
2017-03-09 20:15:32.557037 | from neutron import context as ctx
2017-03-09 20:15:32.557060 | ImportError: cannot import name context

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/443960
Committed: https://git.openstack.org/cgit/openstack/networking-powervm/commit/?id=f1ac6dcad9ccd137017ba68b47e5f4f42f7bfbe5
Submitter: Jenkins
Branch: stable/ocata

commit f1ac6dcad9ccd137017ba68b47e5f4f42f7bfbe5
Author: Eric Berglund <email address hidden>
Date: Tue Mar 7 08:53:47 2017 -0600

    Import context from neutron_lib

    The context.py file has been moved from neutron to neutron-lib.
    This updates the import statement accordingly.

    Closes-Bug: #1671628

    Change-Id: I061c0b64e19f1daedb506f3a4cc34edfc6306b4c
    (cherry picked from commit 240fa28d66288e3890738d414fd4a6fab997f53e)