Reset CONF for topology_helper and services during unit tests

This commit addresses an intermittent unit test failure by ensuring
that the CONF is reset to its original value after execution of
unit tests that alter it.

Fixes: bug #1263931

Change-Id: I2970f10f677507f413bfe87338fb3e301b9699a4
Merge "Reset CONF for topology_helper and services during unit tests"