Commit a3172027 introduced test_transaction as a requirement for
flushing old lists -- but it can never return 1 unless the transaction
has already been flushed.

As a result, we have a routine that iterates the j_realblocks list but
doesn't actually do anything. Since it's been this way since 2006 and
the latency numbers were what Chris expected, let's just rip it out.
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Signed-off-by: NJan Kara <jack@suse.cz>