Fix SDK exception parsing
Fix SDK exception parsing

There are cases where the exceptions returned from services are not
correctly parsed by either keystoneauth1 or python-openstacksdk.
Fortunately, the sdk code kept the original response instance where we
can parse the content to extract a more precise/useful message.

Change-Id: Ied68ac3b5d6b75cab6bd72ff944d302aca6c3585
Closes-Bug: #1515108

tengqm/senlin-container,openstack/senlin,stackforge/senlin,openstack/senlin,stackforge/senlin,openstack/senlin,tengqm/senlin-container