register an unittest handler for testresults and expose it as
variable result.
With this even partial results from an interrupted test suite run
can be made available
(From OE-Core rev: a97ae47525157871b6c098ffc352293e365a4335)
Signed-off-by: Konrad Weihmann <kweihmann@outlook.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>