Use Resource class from Oslo

Most methods of Resource class from keystoneclient are similar to methods
from common code.
In the process of unification of the clients code we should
reuse common functionality from Oslo.

Related to blueprint common-client-library-2

Change-Id: I5858eec1596a6921dcf49dfcefb7abd4387de73b
Merge "Use Resource class from Oslo"
Test commit