fix memory leak in g_bio zone introduced in r320452, another ABD fallout

I overlooked the fact that that ZIO_IOCTL_PIPELINE does not include
ZIO_STAGE_VDEV_IO_DONE stage. We do allocate a struct bio for an ioctl
zio (a disk cache flush), but we never freed it.

This change splits bio handling into two groups, one for normal
read/write i/o that passes data around and, thus, needs the abd data
tranform; the other group is for "data-less" i/o such as trim and cache
flush.

PR: 222288
Reported by: Dan Nelson <dnelson@allantgroup.com>
Tested by: Borja Marcos <borjam@sarenet.es>
MFC after: 10 days