jbd2: 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 expicit sync/umount happens.

Signed-off-by: Alex Zhuravlev (Tomas) <alex.zhuravlev@sun.com>
Signed-off-by: Andreas Dilger <adilger@sun.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>