NFS: Fix /proc/mount for legacy binary interface

Add a flag so we know if we mounted the NFS server using the legacy
binary interface.  If we used the legacy interface, then we should not
show the mountd options.

Signed-off-by: Bryan Schumaker <bjschuma@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>