Fall back to UUID when delete by name fails
Fall back to UUID when delete by name fails

Because pre-Ocata congress-server did not support
datasource delete by name(+), client code that attempts
to delete by name(++) fails with pre-Ocata server

This patch fixes the regression by falling back to
delete by UUID when delete by name fails.

For backward compatibility with pre-Ocata congress-server
that does not have this patch:

(+) added in this patch:
https://review.openstack.org/#/c/412303/

(++) introduced in this patch:
https://review.openstack.org/#/c/407329/

Change-Id: Ib8a86304bcff70b9e777d6923d0eaf88cbce7d60

openstack/python-congressclient