Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

zfs: add ztest to the kyua test suite.

This program is currently failing, and has been for >6 months on HEAD.
Ideally, this should be run 24x7 in CI, to discover hard-to-find bugs that
only manifest with concurrent i/o.

Requested by: lwhsu, mmacy