minidump: a hack to prevent vm_page_dump bitmap change during dumping

[perryh at pluto.rain.com]

Matthew Jacob <mj at feral.com> wrote:

> ... IMO, the best thing to do is to when 
> you're panicing stop all other CPUs.

which is fine _if_ the system is healthy enough to do it.
If it's unhealthy enough to be panicing, it may not be
healthy enough to be doing IPC operations.