mount: copy the port field into the cloned nfs_server structure.

Doing this copy eliminates the "port=0" entry in
the /proc/mounts entries

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=69241



Signed-off-by: Steve Dickson <steved@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>