JBD: round commit timer up to avoid uncommitted transaction

Fix jiffie rounding in jbd commit timer setup code.  Rounding down could cause
the timer to be fired before the corresponding transaction has expired.  That
transaction can stay not committed forever if no new transaction is created or
explicit sync/umount happens.

Signed-off-by: Andreas Dilger <adilger@sun.com>
Signed-off-by: Jan Kara <jack@suse.cz>