MFC r208300: Fix a race between ngs_rcvmsg() and soclose() which closes the control socket while it is still in use as ngs_rcvmsg() runs without any lock held.
MFC r208300:
Fix a race between ngs_rcvmsg() and soclose() which closes the control
socket while it is still in use as ngs_rcvmsg() runs without any lock
held.

Sponsored by:	Sandvine Incorporated
Approved by:	re (bz)

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