[pnfs] [0/1] Fix layoutget export ops for d13

[seattleplus at gmail.com]

The structures passed between nfsd and the file
system did not reflect the new concept of putting
a single layoutid in a file layout and a start
server.  This patch updates the data structures
(nfsd4_pnfs_filelayout is now pnfs_filelayout_layout)
and functions for this new way of representing
the file layout.