Unlinked files don't respect synchronous flush commands, but when they get relinked
their state is unknown. Previously we force flushed all such files even when
sync=disabled. Correct this case.
Reviewed-by: Chunwei Chen <tuxoko@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Signed-off-by: DHE <git@dehacked.net>
Closes#10005