In preparation for 10.3-RELEASE, temporarily revert the MFC of r291244
done as part of r292895 on stable/10 as that change causes hangs with
ZFS and the cause on at least amd64 so far not understood.
Discussed with: kib
For further information see:
https://lists.freebsd.org/pipermail/freebsd-stable/2016-February/084045.html

PR: 207281
Approved by: re (gjb)