nvme: flush scan work on passthrough commands

If a passthrough command causes the namespace inventory or capabilities
to change, flush the scan work that handles these changes so the driver
synchronizes with the user command's effects before returning the result
to user space.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>