resulttool: Prevent multiple results for the same test

resulttool: Prevent multiple results for the same test

Currently, if a test occurs multiple times over different series, the
code will sum these.  This can lead to confusion over the desired
results.  Change the code to report the redundant tests and skip adding
an additional values.

(From OE-Core rev: caeaa0648dff64c56a33f52e45e82bfab6719e3e)

Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>