upstream_ha: Fixed extra parameters storage

The extra parameters of an upstream were stored as cfl_variant,
but retrieved as strings (char *) in out_forward.

This would lead to errors when using "Compress gzip" in an
upstream configuration file for out_forward, for example:
[error] [output:forward:forward.0] invalid compress mode: ☺

Signed-off-by: Benoît GARNIER <[email protected]>

src/flb_upstream_ha.c

@@ -241,7 +241,7 @@ static struct flb_upstream_node *create_node(int id,
         key[klen] = '\0';
 
         /* Add the key and value to the hash table */
-        ret = flb_hash_table_add(ht, key, klen, entry->val, vlen);
+        ret = flb_hash_table_add(ht, key, klen, entry->val->data.as_string, vlen);
         if (ret == -1) {
             flb_error("[upstream_ha] cannot add key %s to hash table",
                       entry->key);