multiple instances of the same lock_owner when a process both
inherited an open file descriptor plus opened the same file itself.
Since some NFSv4 servers cannot handle multiple instances of
the same lock_owner string, this patch changes the algorithm
used by nfscl_getopen() in the new NFSv4 client to keep that
from happening. The new algorithm is simpler, since there is
no longer any need to ascend the process's parentage tree because
all NFSv4 Closes for a file are done at VOP_INACTIVE()/VOP_RECLAIM(),
making the Opens indistinct w.r.t. use with Lock Ops.
This problem was discovered at the recent NFSv4 interoperability
Bakeathon.
MFC after: 2 weeks
98a7b279a2