kernel - Correct bug in malloc_type ks_memuse/ks_inuse management

kernel - Correct bug in malloc_type ks_memuse/ks_inuse management

* The new kfree() was improperly adjust ks_memuse/ks_inuse for the wrong
  cpu, leading to MP races which could cause the memory statistics to go
  negative and trigger a panic.

* When calculating loosememuse it is possible to race another cpu and
  come up with an incorrect value.  The race itself is ok, loosememuse
  is not supposed to be 100% deterministic, but even so do not allow
  the value to underflow or we will wind up asserting.