rpc/client: Dial with grpc.WithReturnConnectionError option

Since 2b89b7e, RPC client used
`grpc.WithBlock` option to dial the server. This option make dialer to
return either `nil` or `context.DeadlineExceeded` errors, with any
connection error resulting in the latter. In particular, TLS handshake
failures were shadowed by deadline error.

Now `WithReturnConnectionError` option is used instead:
 * it still blocks similar to `WithBlock`;
 * it adds connection failure to the deadline error.

As a result, TLS unit test passes now. This should fix the problem
originally posted in nspcc-dev/neofs-node#2561.

Signed-off-by: Leonard Lyubich <leonard@morphbits.io>

rpc/client/connect.go

@@ -53,7 +53,7 @@ func (c *Client) openGRPCConn(ctx context.Context, extraDialOpts ...grpcstd.Dial
 
 	dialOpts := []grpcstd.DialOption{
 		grpcstd.WithTransportCredentials(creds),
-		grpcstd.WithBlock(),
+		grpcstd.WithReturnConnectionError(),
 	}
 	if extraDialOpts != nil {
 		dialOpts = append(dialOpts, extraDialOpts...)