Fix zfs send -v, -P, -n, and -V again

[sef]

Summary

avg@ noted that r344601 (which added -V, setting the process title during zfs send) had broken some of the output expected. He was right. It was a bone-head error on my part.

This seems to fix it. But let's try to get some reviews on it, I say.

Test Plan

Create a snapshot on a ZFS dataset, let's call it tank@SNAP1. Then check the following all behave as expected:

zfs send -n -v -P tank@SNAP1
zfs send -V -v -P tank@SNAP1 # note we need to send data, so we can check via ps that the process title has changed
zfs send -n -v tank@SNAP1

[avg]

A general comment: I hope the current review summary will not be a commit message :)

[avg]

The change itself looks good to me.
Thank you!