pom: update to nfs4j-0.9.1

Changelog for nfs4j-0.9.0..nfs4j-0.9.1
    * [8ff8ff0] vfs-cache: add a possibility to cache FsStat results
    * [db7873f] vfs-cache: do not use memoizeWithExpiration if cachelifetime is
    * [25a1079] nfsv3: remove useless lookup and getattr on remove
    * [41dea07] calculate index in the FsExport constructor

Acked-by: Paul Millar
Target: master, 2.10
Require-book: no
Require-notes: no