libs: update nfs library

bugfix version:

Changelog for nfs4j-0.6.2..nfs4j-0.6.3
    * [ebf7974] nfsv3: fix hard link creation (similar to http://rb.dcache.org/r/6224)

Acked-by: Paul Millar
Target: master, 2.7, 2.6
Require-book: no
Require-notes: no