knotty: Fix output buffering issues

knotty: Fix output buffering issues

We need to flush the footer removal, else it may not be outputted until
the buffer is flushed as part of StreamHandler and this would lead to
it removing the ERROR output just printed which is extremely confusing.

Also ensure the footer is cleared before printing a summary as in
some cases it wasn't being removed, also leading to user confusion.

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