contrib.openstack.amulet.utils imports removed novaclient.v1_1 module

Whilst running tests on ceilometer on Xenial I ran into:

./tests/015-basic-trusty-icehouse
Traceback (most recent call last):
  File "./tests/015-basic-trusty-icehouse", line 5, in <module>
    from basic_deployment import CeilometerBasicDeployment
  File "/home/ubuntu/charms/trusty/ceilometer-dtag/ceilometer/tests/basic_deployment.py", line 11, in <module>
    from charmhelpers.contrib.openstack.amulet.utils import (
  File "/home/ubuntu/charms/trusty/ceilometer-dtag/ceilometer/tests/charmhelpers/contrib/openstack/amulet/utils.py", line 30, in <module>
    import novaclient.v1_1.client as nova_client
ImportError: No module named v1_1.client

This is because the 'v1_1' module has been removed from novaclient for version 3.x+ (previously deprecated).

The fix is to import novaclient.client directly (no v1_1, v2, etc.) and in the client.Client() instantiation, reference the required protocol ("2" in this case).