Revision 332572

Merge r331871:
  Handle a special case when a slab can fit only one allocation,
  and zone has a large alignment. With alignment taken into
  account uk_rsize will be greater than space in a slab. However,
  since we have only one item per slab, it is always naturally
  aligned.

  Code that will panic before this change with 4k page:

        z = uma_zcreate("test", 3984, NULL, NULL, NULL, NULL, 31, 0);
        uma_zalloc(z, M_WAITOK);

  A practical scenario to hit the panic is a machine with 56 CPUs
  and 2 NUMA domains, which yields in zone size of 3984 (on head).

PR:		227116