kern/189355: zfs panic on 10-stable

[Radim Kolar]

> This could be something that has already has a fixed in head but wasn't expected
> to get triggered without TRIM queueing which isn't in 10-stable yet. The fix
> is also likely to change based on feedback from the openzfs guys, hence isn't
> in 10-stable yet.

only workaround to get 10-STABLE boot without panic is to boot 10.0 and then import/export pool.

265046 is already merged in 10-stable.
Now building stable with 265152 and 265321 merged.