libyang REFACTOR prefix format always decides the callback (#1169)

So the callback is no longer needed as a parameter.
Also, union no longer uses its own prefix mappings
but instead uses the original format and copies any
required prefix data.
diff --git a/tools/re/main.c b/tools/re/main.c
index 01e45c4..2ed63db 100644
--- a/tools/re/main.c
+++ b/tools/re/main.c
@@ -273,7 +273,7 @@
     }
 
     type = ((struct lysc_node_leaf*)mod->compiled->data)->type;
-    match = type->plugin->store(ctx, type, str, strlen(str), 0, NULL, NULL, LYD_XML, NULL, NULL, NULL, NULL, &err);
+    match = type->plugin->store(ctx, type, str, strlen(str), 0, LY_PREF_JSON, NULL, NULL, NULL, NULL, NULL, &err);
     if (verbose) {
         for (i = 0; i < patterns_count; i++) {
             fprintf(stdout, "pattern  %d: %s\n", i + 1, patterns[i]);