NLM: Don't hang forever on NLM unlock requests

If the NLM daemon is killed on the NFS server, we can currently end up
hanging forever on an 'unlock' request, instead of aborting. Basically,
if the rpcbind request fails, or the server keeps returning garbage, we
really want to quit instead of retrying.

Tested-by: Vasily Averin <vvs@sw.ru>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@kernel.org
const char *rpc_peeraddr2str(struct rpc_clnt *clnt,
			     enum rpc_display_format_t format)
{
	struct rpc_xprt *xprt = clnt->cl_xprt;

	if (xprt->address_strings[format] != NULL)
		return xprt->address_strings[format];
	else
		return "unprintable";
}

const char *rpc_peeraddr2str(struct rpc_clnt *clnt,
			     enum rpc_display_format_t format)
{
	struct rpc_xprt *xprt = clnt->cl_xprt;

	if (xprt->address_strings[format] != NULL)
		return xprt->address_strings[format];
	else
		return "unprintable";
}
