o Modify nfslockdans() to accept a thread reference instead of a proc

o Modify nfslockdans() to accept a thread reference instead of a proc
  reference: with td->td_ucred, it will be desirable to authorize
  based on td->td_ucred, rather than p->p_ucred.
o Since the same variable 'p' was later used with pfind() on the target
  process for the wakeup, introduce a new local variable 'targetp'
  to use instead.

Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, NAI Labs