In mountd, if get_exportlist() (utils/mountd/mountd.c) returns NULL it

In mountd, if get_exportlist() (utils/mountd/mountd.c) returns NULL it
should not be considered a failure. It just means that there are no
exports on the system.

The practical problem with the current code is that a showmount -e
results in a syslog message from mountd that looks like:

rpc.mountd: export request from 10.250.100.2 failed.

Reviewed-by: Greg Banks <gnb@sgi.com>
Signed-off-by: Harshula Jayasuriya <harshula@sgi.com>
Signed-off-by: Steve Dickson <steved@redhat.com>