Temporarily disable Direct IO by default
While some remaining issues are resolved with the recently merged
Direct IO functionality disable it by default.
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Brian Atkinson <batkinson@lanl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #16597