parser xml BUGFIX full xml context backup

... including opened elements and namespaces.
Fixes cesnet/netopeer2#930
diff --git a/tests/utests/data/test_parser_xml.c b/tests/utests/data/test_parser_xml.c
index b83432c..1e74bb9 100644
--- a/tests/utests/data/test_parser_xml.c
+++ b/tests/utests/data/test_parser_xml.c
@@ -251,6 +251,13 @@
     CHECK_LYD_STRING(tree, LYD_PRINT_WITHSIBLINGS, "<foo3 xmlns=\"urn:tests:a\"/>\n");
     lyd_free_all(tree);
 
+    /* list, opaq flag */
+    data = "<l1 xmlns=\"urn:tests:a\"/>";
+    CHECK_PARSE_LYD(data, LYD_PARSE_OPAQ | LYD_PARSE_ONLY, 0, tree);
+    CHECK_LYD_NODE_OPAQ((struct lyd_node_opaq *)tree, 0, 0, LY_VALUE_XML, "l1", 0, 0, NULL,  0,  "");
+    CHECK_LYD_STRING(tree, LYD_PRINT_WITHSIBLINGS, "<l1 xmlns=\"urn:tests:a\"/>\n");
+    lyd_free_all(tree);
+
     /* missing key, no flags */
     data = "<l1 xmlns=\"urn:tests:a\">\n"
             "  <a>val_a</a>\n"