bitcoin-cli: rename bcli_args() to bcli_args_direct(), and also warp it in bcli_args()

1. bcli_args_direct() will be used in wait_for_bitcoind;
At the beginning, we check if bitcoin-cli is running by "echo" command
whitout any bitcoin_cli struction. If this first command fails, we need
present the agrs gathered, like "-rpcuser", like "-rpcpassword".
Related changes include:
  i) rename bcli_args() to bcli_args_direct(), and use 'const char **'
      as the paramater for bcli_args_direct();
  ii) add a new function bcli_args() warpped on bcli_args_direct(), this
      warpping can reduce the large number of changes later in the file;
2. bcli_args() warpping on bcli_args_direct() is used like original.

lightningd/bitcoind.c

@@ -111,24 +111,32 @@ static struct io_plan *output_init(struct io_conn *conn, struct bitcoin_cli *bcl
 static void next_bcli(struct bitcoind *bitcoind, enum bitcoind_prio prio);
 
 /* For printing: simple string of args. */
-static char *bcli_args(const tal_t *ctx, struct bitcoin_cli *bcli)
+/* bcli_args_direct() will be used in wat_for_bitcoind(), where
+ * we send bitcoin-cli a "getblockchaininfo" command without
+ * struct bitcoin_cli */
+static char *bcli_args_direct(const tal_t *ctx, const char **args)
 {
 	size_t i;
-	char *ret = tal_strdup(ctx, bcli->args[0]);
+	char *ret = tal_strdup(ctx, args[0]);
 
-	for (i = 1; bcli->args[i]; i++) {
+	for (i = 1; args[i]; i++) {
             ret = tal_strcat(ctx, take(ret), " ");
-            if (strstarts(bcli->args[i], "-rpcpassword")) {
+            if (strstarts(args[i], "-rpcpassword")) {
                     ret = tal_strcat(ctx, take(ret), "-rpcpassword=...");
-            } else if (strstarts(bcli->args[i], "-rpcuser")) {
+            } else if (strstarts(args[i], "-rpcuser")) {
                     ret = tal_strcat(ctx, take(ret), "-rpcuser=...");
             } else {
-                ret = tal_strcat(ctx, take(ret), bcli->args[i]);
+                ret = tal_strcat(ctx, take(ret), args[i]);
             }
 	}
 	return ret;
 }
 
+static char *bcli_args(const tal_t *ctx, struct bitcoin_cli *bcli)
+{
+    return bcli_args_direct(ctx, bcli->args);
+}
+
 static void retry_bcli(struct bitcoin_cli *bcli)
 {
 	list_add_tail(&bcli->bitcoind->pending[bcli->prio], &bcli->list);