filter log size in 206

filter log size in 206

With the log size now going past 128MB, test 206 creates a filesystem
with a much larger log than 128MB. The golden output expects at
128MB log size, so the test breaks. Filter the log size out of the
mkfs output and golden output so that the test works on both older and
newer mkfs binaries.

Signed-off-by: Dave Chinner <david@fromorbit.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>