jbd2: use SWRITE_SYNC_PLUG when writing synchronous revoke records

jbd2: use SWRITE_SYNC_PLUG when writing synchronous revoke records

The revoke records must be written using the same way as the rest of
the blocks during the commit process; that is, either marked as
synchronous writes or as asynchornous writes.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>