Remove $FreeBSD$: one-line sh pattern

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

pkgbase: Create a FreeBSD-nfs package

And move all the nfs related commands there.

Reviewed by: emaste
Differential Revision: https://reviews.freebsd.org/D30754
Sponsored by: Diablotin Systems

Add a command that disables a pNFS server mirrored DS.

This command can be used by a sysadmin to disable a malfunctioning pNFS server
mirrored DS. It is safe to use when a mirrored DS has already been disabled
via an I/O or network partitioning error.