Minor fix to keep pynfs test suite happy
Changelog for nfs4j-0.18.0..nfs4j-0.18.1
* [638910f] [maven-release-plugin] prepare for next development iteration
* [3ad8698] nfs4: check for invalid attribute prior VERIFY/NFERIVY
* [b89a200] [maven-release-plugin] prepare release nfs4j-0.18.1
