SUNRPC: rpcb_getport_sync() should use built-in hostname generator

rpc_create() can already fill in the hostname with a string representation
of the server's IP address, so remove redundant logic in in
rpcb_getport_sync() that does that.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>