Commit b9de4087685 (memory: Avoid an empty log message if there's nothing
to log.) introduced a 100% CPU usage condition when there is nothing to
log. This fixes the problem.
Reported-by: Ansis Atteka <aatteka@nicira.com>
Acked-by: Ansis Atteka <aatteka@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>