SUNRPC: fix bug in patch "portmapper doesn't need a reserved port"

 The in-kernel portmapper does in fact need a reserved port when registering
 new services, but not when performing bind queries.

 Ensure that we distinguish between the two cases.

Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>