This information will be used to determine which layout driver,
if any, to use for subsequent IO on this filesystem.  Each driver
is assigned an integer id, with 0 reserved to indicate no driver.

The server can in theory return multiple ids.  However, our current
client implementation only notes the first entry and ignores the
rest.
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>