zfsbootcfg(8), zpool_influxdb(8): move to the zfs package

These tools are only useful on a system running ZFS.

Reviewed by: imp, manu
Pull Request: https://github.com/freebsd/freebsd-src/pull/1175

Remove $FreeBSD$: one-line sh pattern

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

zfs: attach zpool_influxdb to build

From the zpool_influxdb.8 manual page:
zpool_influxdb produces InfluxDB-line-protocol-compatible metrics from
zpools. Like the zpool command, zpool_influxdb reads the current pool
status and statistics. Unlike the zpool command which is intended for
humans, zpool_influxdb formats the output in the InfluxDB line protocol.
The expected use is as a plugin to a metrics collector or aggregator,
such as Telegraf.

zpool_influxdb is installed into /usr/libexec/zfs/

Differential revision: https://reviews.freebsd.org/D31094
MFC after: 3 days