parse_stream_outer used to convert a exit value to a return code,
but parse_stream_outer maybe inside a recursion. This means that
the exit status is lost in this case. Test case:

if [ 0 = 0 ]; then
	false
	exit $?
fi

echo "shouldn't be here"

Without this patch "shouldn't be here" will be printed.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>