This is an additional tool, and this function is executed on source
time so we'd spew errors.
(also remove an ineffective line - it's probably *nicer* with the
read, but that's not what's currently effectively doing anything)
Under FreeBSD, as annoying as it is, switches must directly follow the
command or subcommand in question, and cannot come after actual payload
argument. Calling `zpool get all -H` instead of `zpool get -H all`
caused error messages to be spewed to the console under FreeBSD when
simply completing `zfs <TAB>`, this should fix that. The change should
also be compatible with other operating systems (namely Linux) that
don't have this requirement, as they (generally) allow arguments to come
before _or_ after the primary non-switch argument (though I do not have
access to a zfs-enabled Linux machine to test this).