kernel - Change lwkt_wait_ipiq() to use the TSC

* lwkt_wait_ipiq() was using a static counter/constant for its failsafe
  panic, which can vary immensly over time and might not be long enough
  for systems running under VMs.

* Change the code to use the TSC api to properly time the failsafe.  It
  will generate warnings each second and panic at 10 seconds if the IPIQ
  fails to drain.

Reported-by: marino