We've seen hard to debug issues where a task ends up in both the
covered and notcovered list. Add a sanity check to ensure if this
happens in future, we see it in the logs.
(Bitbake rev: 6e001410854792f9bb66a0409a2ac176171b0507)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>