MFC r196159:   Drain link state event changes posted during vap destroy.  This is a   band-aid for the general problem that if_link_state_change can be   called between if_detach and if_free leaving a task queued that has   been free'd.
MFC r196159:
  Drain link state event changes posted during vap destroy.  This is a
  band-aid for the general problem that if_link_state_change can be
  called between if_detach and if_free leaving a task queued that has
  been free'd.

Reviewed by:	rwatson
Approved by:	re (rwatson)

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