param: consistent callback format

The `json_tok_X` functions now consistently check the success case first
and call `command_fail` at the end.

Signed-off-by: Mark Beckwith <wythe@intrig.com>

lightningd/json.c

@@ -120,13 +120,13 @@ bool json_tok_double(struct command *cmd, const char *name,
 		     double **num)
 {
 	*num = tal(cmd, double);
-	if (!json_to_double(buffer, tok, *num)) {
+	if (json_to_double(buffer, tok, *num))
+		return true;
+
 	command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 		     "'%s' should be a double, not '%.*s'",
 		     name, tok->end - tok->start, buffer + tok->start);
 	return false;
-	}
-	return true;
 }
 
 bool json_tok_number(struct command *cmd, const char *name,
@@ -134,13 +134,13 @@ bool json_tok_number(struct command *cmd, const char *name,
 		     unsigned int **num)
 {
 	*num = tal(cmd, unsigned int);
-	if (!json_to_number(buffer, tok, *num)) {
+	if (json_to_number(buffer, tok, *num))
+		return true;
+
 	command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 		     "'%s' should be an integer, not '%.*s'",
 		     name, tok->end - tok->start, buffer + tok->start);
 	return false;
-	}
-	return true;
 }
 
 bool json_tok_sha256(struct command *cmd, const char *name,
@@ -164,13 +164,13 @@ bool json_tok_u64(struct command *cmd, const char *name,
 		  uint64_t **num)
 {
 	*num = tal(cmd, uint64_t);
-	if (!json_to_u64(buffer, tok, *num)) {
+	if (json_to_u64(buffer, tok, *num))
+		return true;
+
 	command_fail(cmd, JSONRPC2_INVALID_PARAMS,
 		     "'%s' should be an unsigned 64 bit integer, not '%.*s'",
 		     name, tok->end - tok->start, buffer + tok->start);
 	return false;
-	}
-	return true;
 }
 
 bool json_to_pubkey(const char *buffer, const jsmntok_t *tok,