This finishes what r245164 started and makes open(..., O_APPEND) work again
after r299753.
- Pass ioflags, incl. IO_APPEND, down to the direct write backend (r245164
added it to only the bio backend).
- (r299753 changed the WRONLY backend from bio to direct.)
PR: 220185
Reported by: Ben RUBSON <ben.rubson at gmail.com>
Reviewed by: bapt@, rmacklem@
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D11348
f2c2576539