Fix inheritance order in BaseTestCase

With release of testtools 1.4.0 test ids do not contain test attrs anymore.
It is related to improper MRO.

Make proper inheritance order,
remove testresources dependency as unused,
add unit tests.

Corresponding fix in Tempest: 2474f41f10808c7283778b96f8693238ea21297f

Change-Id: Ife208c6e74f18bdcd86e47b05caad6dc8f53d779
Closes-Bug: #1398487