data_smart: Fix variable reference issues

The change to use the expansion cache in VariableParse was incorrect as
it was adding in references it shouldn't have been. This patch corrects
the codepaths and ensures the references are correct.

The cache version is bumped since the previous bug could have leave
to invalid checksum calculations and a clean cache is therefore desireable.

The impact of the bug was that sstate was not getting reused when it should
and some tasks were also being rerun when they should not have been.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>