libs: update to nfs4j-0.7.8

performance improvements

Changelog for nfs4j-0.7.7..nfs4j-0.7.8
    * [c885cc0] pseudofs: do not check READ_ATTR bit for unix
    * [787ddaf] avoid extra copy of data buffer in nfs3.read

Target: 2.8, 2.7, 2.6
Require-book: no
Require-notes: no
Merge pull request #1043 from kofemann/update-nfs-2.6

libs: update to nfs4j-0.7.8