The VM host might send multiple messages at once but vmt(4) only

The VM host might send multiple messages at once but vmt(4) only
processed one of time per second.  Change the code to process all
queued messages without delay immediately.  This fixes two things: a)
the vmt time sensor is available on boot when ntpd -s is loaded and b)
the random seeding on resume (OS_Resume message) is executed almost
immediately and not delayed by about 20 seconds.

ok deraadt@