Make it a struct cmd_header, since that's what it is, and clean up
the places that it's used.
Signed-off-by: NDan Williams <dcbw@redhat.com>
Signed-off-by: NDavid Woodhouse <dwmw2@infradead.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>