This fixes some performance problems.  Some vendors implement firmware
updates over IPMI, and this speeds up that process quite a bit.

 * Improve the "send - wait for response - send -wait for response -
   etc" performance when using high-res timers.  Before, an ~10ms delay
   would be added to each message, because it didn't restart the timer
   if nothing was happing when a new message was started.

 * Add some checking for leaked messages.