oetest: Drop getResults usage from oeRuntimeTest

oetest: Drop getResults usage from oeRuntimeTest

Despite the name, this code is only used from testexport and the function
in question is broken on python 3.8 onwards. Since nobody is using it
and the failure log handling here is of questionable benefit anyway, drop it.
We should be using the same code for normal test runs and testexport,
not having two different codepaths.

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