Don't give client an empty flavor list

Don't give client an empty flavor list

In the absence of an explicit sec= option on an export, rpc.mountd
is returning a zero-length flavor list to clients in the MOUNT results.

The linux client doesn't seem to mind, but the Solaris client
(reasonably enough) is giving up; the symptom is a "security mode
does not match" error on mount.

We could modify the export-parsing code to ensure the secinfo array
is nonzero.  But I think it's slightly simpler to handle this default
case in the implementation of the MOUNT call.  This is more-or-less the
same thing the kernel does when mountd passes it an export without any
security flavors specified.

Thanks to Tom Haynes for bug report and diagnosis.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Steve Dickson <steved@redhat.com>