Replace the open code to construct SM_NOTIFY and PMAP_GETPORT RPC
requests with calls to our new library routines that support
IPv6 and RPCB_GETADDR as well.
This change allows sm-notify to send RPCB_GETADDR, but it won't do
that until the main sm-notify socket supports PF_INET6 and the DNS
resolution logic is updated to return IPv6 addresses.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>