RPM - Refactor config code and ensure unittests work

It appears that calling the unit tests outside of the rpm folder results
in them failing. This is due to the relative path of the config file.

Also refactored the uses of config so all accesses are done through the
config class.

BUG=chromium-os:37989
TEST=ensured the unit tests work inside and outside the rpm_control_system
folder.

Change-Id: Ia7d4d3dcdc4e67cd71a0494fcb40b7d959f9805c
Reviewed-on: https://gerrit.chromium.org/gerrit/43195
Reviewed-by: Scott Zawalski <scottz@chromium.org>
Commit-Queue: Simran Basi <sbasi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
2 files changed