libs: update to nfs4j-0.7.6

Changelog for nfs4j-0.7.5..nfs4j-0.7.6
    * [8e982e5] acl: fix permission check on listdirectory
    * [8c8ecec] mount: add support for symlinks

Target: 2.6, 2.7, 2.8
Require-book: no
Require-notes: yes
Merge pull request #792 from kofemann/nfs4j-0.7.6-2.8

libs: update to nfs4j-0.7.6