drop cherry-pick workarounds
drop unneeded/non-upstream pull requests:
- #1099: iSCSI support for ZoL
- #1476: Change sharesmb to use REGISTRY shares for better
control by user/admin
- #2790: Rewrite of nfs.c to keep options per host separated.
- #3238: Allow "zfs unshare <proto> -a" much like "zfs share
<proto> -a" (WIP)