libs: update to bugfix nfs4j-0.7.3

Changelog for nfs4j-0.7.2..nfs4j-0.7.3
    * [f2b0d2b] vfs: fix regression introduced in 1c916c5

Acked-by: Gerd Behrmann
Target: master, 2.8, 2.7
Require-book: no
Require-notes: no