Remove $FreeBSD$: one-line sh pattern

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

Multiple fixes to the zfsd test suite

* Wait for gnop devices to disappear after "gnop destroy".

Apparently that process is asynchronous now, or maybe it's just slower
than it used to be. Also, after removing a gnop wait for its pool to
be degraded. That isn't instant.

* The zfsd tests no longer require camcontrol.

This was a harmless oversight from
11ed0a95bfa76791dc6428eb2d47a986c0c6f8a3

* Fix the zfsd_degrade_001_pos test for recent zfs versions.

ZFS now rate limits checksum errors to about 20 per second. But
zfsd's threshold for degrading a disk is 50 per minute. So we must
alternately corrupt and scrub the pool to ensure that checksum errors
are generated in multiple 1-second windows, so that zfsd will see
enough of them.

* Fix the zfsd_fault_001_pos test in VMs

And, for that matter, when using NVME or SATA disks. As originally
written, the test used the da driver to inject errors. Rewrite it to
use gnop vdevs. gnop can also inject errors. It works on top of any
disk device, and it's also faster than using da.

MFC after: 2 weeks
Sponsored by: Axcient
Differential Revision: https://reviews.freebsd.org/D39437

Add the ZFS test suite

It was originally written by Sun as part of the STF (Solaris test framework).
They open sourced it in OpenSolaris, then HighCloud partially ported it to
FreeBSD, and Spectra Logic finished the port. We also added many testcases,
fixed many broken ones, and converted them all to the ATF framework. We've had
help along the way from avg, araujo, smh, and brd.

By default most of the tests are disabled. Set the disks Kyua variable to
enable them.

Submitted by: asomers, will, justing, ken, brd, avg, araujo, smh
Sponsored by: Spectra Logic Corp, HighCloud