For the INP_TIMEWAIT case, there is no valid tcpcb object tied to the

For the INP_TIMEWAIT case, there is no valid tcpcb object tied to the
inpcb object.
Skip the TCP_SIGNATURE check in that case as it is consistent with the
output path (no TCP_SIGNATURE for outcoming packets in TIMEWAIT state)
and also because for TIMEWAIT state the verify may be less effective.

Sponsored by:		Sandvine Incorporated
Reported by:		rwatson
No objections by:	rwatson
MFC after:		3 days