make sillyrename (try to) use LINK operation rather than RENAME.
PR/33861 from Jed Davis. he provided the almost same patch.
according to him, it also happen to be what opensolaris does in this case.
from the PR:
> In nfs_rename(), if the destination appears to exist and is "in use"
> (this check is apparently satisfied even if the file isn't in use by
> anything except the rename itself), it will sillyrename it, then delete
> the sillyrenamed file even if the rename fails -- for instance, because
> the "from" file no longer exists on the server.
> mkdir a b; touch a/x; perl -e 'fork(); rename("a/x","b/x") or die "$!\n"'
>
> Afterwards, neither a/x nor b/x will exist.
> 1) Lookup of b/x; fails with NOENT.
> 2) Rename from a/x to b/x; succeeds.
> 3) Lookup of b/x; fails with NOENT.
> 4) Rename from b/x to b/.nfsA23a3; succeeds.
> 5) Rename from a/x to b/x; fails with NOENT.
> 6) Remove of b/.nfsA23a3; succeeds.
e38f237e53